Heat the oven to 350°F (175°C). Grease three 9-inch round cake pans and line the bottoms with parchment.

Cream the softened butter and granulated sugar for 3–5 minutes, until light and fluffy. Beat in the eggs one at a time, mixing well after each addition, then stir in the vanilla.

Whisk together the flour, baking soda, and salt. Add the dry mixture to the butter mixture in three additions, alternating with the buttermilk, and mix only until combined.

Fold in the finely chopped pecans, raisins, and coconut. Divide the batter evenly among the prepared pans.

Bake for 25–30 minutes, until the centers spring back lightly and a toothpick inserted in the middle comes out with a few moist crumbs. Cool in the pans for about 10 minutes, then turn the layers onto racks and cool completely.

For the filling, combine the sugar, evaporated milk, and butter in a saucepan over medium heat. Stir constantly until the butter melts and the mixture reaches a gentle simmer.

Cook the filling for approximately 5–7 minutes, stirring frequently, until slightly thickened. Remove from the heat, stir in the pecans, raisins, and coconut, and cool until spreadable.

Place one cake layer on a serving plate and spread approximately one-third to one-half of the filling over it. Add the second layer and repeat, then top with the final layer and spread the remaining filling over the top.

Let the assembled cake stand for several hours, preferably overnight, before slicing. Refrigerate it overnight for the cleanest cuts, then bring it close to room temperature before serving.