Step 1

Preheat oven to 350 degrees F. Coat 3 (8-inch) round cake pans with cooking spray and sprinkle with flour. (Yes, 3 layers!)

Step 2

In a large bowl with an electric mixer on medium speed, beat cake mix, eggs, buttermilk, and oil 2 minutes. Stir in coconut and 3/4 cup pecans. Pour batter evenly into cake pans.

Step 3

Bake 16 to 18 minutes or until a toothpick inserted in center comes out clean. Cool in pans on wire racks 10 minutes. Remove from pans and cool completely on wire racks.

Step 4

Sprinkle each cake layer with rum, if desired; let stand 10 minutes.

Step 5

Stir together frosting and remaining 1 cup pecans. Spread frosting between layers and on top and sides of cake (See Tips). Chill 2 hours before slicing.