Heat the oven to 325°F (165°C). Grease and flour a 10-inch Bundt or tube pan thoroughly, making sure the center tube and every decorative groove are coated.

Whisk the all-purpose flour, baking powder, and salt together in a medium bowl. This distributes the leavening and salt evenly before they are added to the batter.

Beat the softened butter and granulated sugar on medium speed for 4 to 6 minutes, until the mixture is very light and fluffy. Scrape the bowl once or twice so the butter creams evenly.

Add the room-temperature eggs one at a time, beating well after each addition. Scrape down the sides of the bowl as needed before adding the next egg.

Mix in the orange zest, fresh orange juice, and vanilla extract until the citrus aroma is evenly distributed. The mixture may look slightly loose, which is fine.

Add the flour mixture in three additions, alternating with the sour cream in two additions. Mix only until the batter is combined, taking care not to overbeat once the flour goes in.

Transfer the batter to the prepared pan and smooth the top with a spatula. Gently tap the pan on the counter once or twice to release any large air pockets.

Bake for 70 to 85 minutes, checking the center with a skewer toward the end of the baking time. The skewer should come out clean or with a few moist crumbs, and the top should be deeply golden.

Cool the cake in the pan for 10 to 15 minutes, then carefully turn it out onto a wire rack. Let it cool completely before glazing so the icing stays thick and visible.

Whisk the confectioners’ sugar with 2 to 3 tablespoons of fresh orange juice, adding the juice gradually until the glaze is thick but pourable. Stir in the optional orange zest, then drizzle it over the cooled cake.