This Key Lime Cake recipe makes a tender, citrusy Southern-style dessert with lemon cake mix, lime gelatin, orange juice, key lime juice, and a rich cream-cheese frosting. The easy cake bakes in a 9 x 13-inch pan in 25 to 30 minutes and yields about 12 servings, making it a practical choice for potlucks, birthdays, holidays, and family dinners.
Every bite has a soft lemon-lime crumb, a gentle floral tartness from key lime juice, and a creamy frosting that balances the bright citrus flavor. A little optional lime glaze can be brushed over the warm cake for extra moisture and a more pronounced key lime finish.
This Key Lime Cake is the kind of dessert that looks festive without requiring complicated cake-decorating skills. The cake mix keeps the preparation quick, while lime gelatin adds color, citrus character, and a tender texture that stays pleasantly moist.
Orange juice is an important part of the flavor profile because it softens the sharper edge of the lime. Together with lemon cake mix and key lime juice, it creates a balanced citrus taste that is tart enough to be refreshing but sweet enough for dessert.
The cream-cheese frosting brings a cool, tangy richness to every slice. It is thick enough for a beautiful layer on a sheet cake and flexible enough to spread between two round layers.
Ready in about 1 1/2 hours, including cooling and frosting.
Makes one 9 x 13-inch cake or two 9-inch round layers.
Serves about 12 people.
Uses easy-to-find ingredients and bottled key lime juice when necessary.
Ingredients You’ll Need
Start with one package of lemon cake mix weighing approximately 15.25 to 18.25 ounces, depending on the brand. Because package sizes vary, choose a package within that range and use only the ingredients listed in this recipe rather than the additional ingredients printed on the box.
The lime gelatin is added directly to the dry cake mix. It contributes a subtle lime flavor and helps give the baked cake its recognizable pale green-gold citrus appearance.
You will also need three large eggs, 1/2 cup vegetable oil, 3/4 cup orange juice, and 1/2 cup key lime juice. Zest from one or two key limes is optional, but it adds fragrant citrus oils and makes the flavor smell especially fresh.
For the frosting, gather 1/2 cup softened unsalted butter, one softened 8-ounce package of cream cheese, one pound of confectioners’ sugar, 1/4 cup key lime juice, and one to two teaspoons of grated lime zest if desired. The optional glaze uses another 1/2 cup key lime juice and 1/2 cup confectioners’ sugar.
How to Make It Step-by-Step
Step 1: Heat the oven to 350°F (175°C) so it is fully ready when the batter is mixed. Grease and flour a 9 x 13-inch pan, or grease and line two 9-inch round cake pans with parchment to make layer removal easier.
Step 2: Add the lemon cake mix and lime gelatin to a large bowl, then whisk or stir them together until evenly distributed. This quick dry mixture helps prevent concentrated pockets of gelatin in the finished cake.
Step 3: Add the eggs, vegetable oil, orange juice, key lime juice, and optional lime zest. Beat the mixture for about 2 minutes, stopping once the batter looks smooth and well blended rather than continuing to mix unnecessarily.
Step 4: Pour the batter into the prepared 9 x 13-inch pan, spreading it into an even layer. If using round pans, divide the batter as evenly as possible so the layers finish at a similar height.
Step 5: Bake the 9 x 13-inch cake for 25 to 30 minutes, or bake the round layers for about 20 to 25 minutes. The cake is ready when the center springs back lightly and a toothpick inserted in the middle comes out clean or with a few moist crumbs.
Step 6: Let the cake cool in the pan for 10 minutes before continuing to cool it completely. If you plan to use the glaze, whisk the key lime juice and confectioners’ sugar together, then spoon or brush it over the warm cake before allowing the cake to cool fully.
Step 7: Make the frosting by beating the softened butter and cream cheese until smooth and creamy. Gradually beat in the confectioners’ sugar, then add the key lime juice and optional zest, mixing until the frosting is thick, creamy, and easy to spread.
Step 8: Frost only after the cake is completely cool, since warm cake can cause cream-cheese frosting to soften and slide. Spread the frosting over the sheet cake, or use it between the round layers and over the top and sides.
Step 9: Chill the frosted cake briefly before slicing if you want especially neat portions. Finish with a little lime zest or thin lime slices, then serve cold or slightly cool for the best contrast between the tender cake and creamy frosting.
Pro Tips for the Best Key Lime Cake
Key limes are small, fragrant, and more floral than standard Persian limes, but they produce very little juice. Bottled key lime juice is a dependable choice for this recipe and makes measuring simple.
If key lime juice is unavailable, regular Persian lime juice can be substituted. The result will still be delicious, though the citrus flavor will be slightly more sharply acidic and less floral.
Bring the butter and cream cheese to room temperature before making the frosting. Soft ingredients blend more evenly, helping you avoid small cream-cheese lumps while you gradually incorporate the confectioners’ sugar.
Measure the cake mix package carefully by choosing a size between approximately 15.25 and 18.25 ounces. Do not add the water, extra eggs, or other ingredients suggested on the box; this recipe has already been balanced with orange juice, key lime juice, oil, and eggs.
For the neatest frosting, refrigerate the completely cooled cake for 20 to 30 minutes before spreading. The cooler surface gives the frosting more support and reduces the chance of soft frosting sliding across the cake.
Sheet Cake or Layer Cake?
The 9 x 13-inch version is the easiest option for casual serving. It travels well in its pan, needs no stacking, and produces generous squares with a good cake-to-frosting ratio.
Two 9-inch round layers make a more traditional celebration cake. Allow the layers to cool completely, spread frosting over the first layer, place the second layer on top, and then cover the top and sides.
When making round layers, begin checking them around 20 minutes because shallower pans can bake more quickly than a deep sheet pan. Use the spring-back and toothpick tests rather than relying on the clock alone.
Storage, Serving, and Make-Ahead Advice
Since the frosting contains cream cheese, cover the cake and refrigerate it. Chilling also firms the frosting and makes the citrus flavor taste especially clean and refreshing.
Let slices stand briefly at room temperature if you prefer a softer crumb, but do not leave the frosted cake out for extended periods. For a party, keep it chilled until close to serving time and garnish just before bringing it to the table.
The unfrosted cake can be cooled, covered, and held until you are ready to decorate. Make the frosting separately, refrigerate it if needed, and let it soften slightly before spreading.
Serve each slice with a small curl of lime zest or a thin lime wedge. The cake needs no reheating, and its cool, creamy texture is part of its appeal.
Common Questions
Can I use regular lime juice? Yes. Persian lime juice works when key lime juice is unavailable, but its flavor is usually sharper and less floral.
Can I skip the optional glaze? Certainly. The cake is moist and flavorful without it, while the glaze provides an extra layer of tart sweetness and moisture.
Can I prepare this as cupcakes? The researched version is designed for a 9 x 13-inch cake or two 9-inch rounds, so baking times and yield would need adjustment for cupcakes. For the most reliable result, use one of the stated pan options.
Key Lime Cake Recipe
A moist Southern-style citrus cake made with lemon cake mix, lime gelatin, orange juice, and key lime juice, finished with tangy cream-cheese frosting. Make it as one 9 x 13-inch cake or two 9-inch round layers.
1packageLemon cake mix, approximately 15.25-18.25 ounces
13-ounce packageLime gelatin
3Large eggs
1/2cupVegetable oil
3/4cupOrange juice
1/2cupKey lime juice
from 1-2key limes, optionalKey lime zest
Cream-Cheese Frosting
1/2cupUnsalted butter, softened
18-ounce packageCream cheese, softened
1pound, about 3 3/4 cupsConfectioners’ sugar
1/4cupKey lime juice
1-2teaspoons, optionalGrated lime zest
Optional Glaze
1/2cupKey lime juice
1/2cupConfectioners’ sugar
Method
Step-by-Step
Heat the oven to 350°F (175°C). Grease and flour one 9 x 13-inch pan, or grease and line two 9-inch round cake pans with parchment.
Combine the lemon cake mix and lime gelatin in a large mixing bowl. Add the eggs, vegetable oil, orange juice, key lime juice, and optional lime zest, then beat for about 2 minutes until smooth and well blended.
Pour the batter into the prepared 9 x 13-inch pan, or divide it evenly between the two round pans. Bake the sheet cake for 25 to 30 minutes, or bake round layers for about 20 to 25 minutes.
Check for doneness when the center springs back lightly and a toothpick comes out clean or with a few moist crumbs. Cool the cake in the pan for 10 minutes, then transfer it to a cooling rack or leave it in the pan until completely cool.
For the frosting, beat the softened butter and cream cheese until smooth. Gradually add the confectioners’ sugar, then beat in the key lime juice and optional zest until creamy.
Spread the frosting over the completely cooled sheet cake, or frost between the round layers and over the top and sides. Chill the cooled cake for 20 to 30 minutes first if the frosting feels difficult to spread.
For the optional glaze, whisk 1/2 cup key lime juice with 1/2 cup confectioners’ sugar and spoon or brush it over the warm cake before cooling and frosting. Slice the finished cake and garnish with lime zest or thin lime slices if desired.
Notes
Use bottled key lime juice when fresh key limes are unavailable; regular Persian lime juice also works but has a sharper, less floral flavor. Do not add the extra ingredients listed on the cake-mix box. Store the frosted cake covered in the refrigerator because the frosting contains cream cheese.
Final Thoughts
This Key Lime Cake recipe brings together the ease of a cake mix and the bright flavor of a classic citrus dessert. Lime gelatin, orange juice, and key lime juice create a soft, fragrant crumb, while the cream-cheese frosting adds just the right amount of tangy richness.
Choose the sheet-cake format for effortless serving or make two round layers when you want a centerpiece dessert. Whether you add the optional glaze or keep the preparation simple, chill the cake before serving and finish it with fresh lime zest for a beautiful final touch.
With about 12 servings and a total preparation time of roughly 1 1/2 hours, this is a dependable fruit dessert for gatherings of almost any size. Keep the cake covered in the refrigerator, then enjoy each cool, creamy, citrus-filled slice.
