For the cake:
- 1 white cake mix , or favorite from-scratch white cake recipe
- 3 eggs
- 1/2 cup oil
- 1/2 cup sour cream
- 1/4 cup key lime juice
- 3/4 cup milk
- 2 tablespoons key lime zest
For the glaze:
- 1/4 cup butter
- 1/4 cup sugar
- 2 tablespoons key lime juice
- 1/2 cup light rum*
For the frosting:
- 1/2 cup butter, softened
- 1/2 cup vegetable shortening
- 1 teaspoon coconut extract
- 1 teaspoon light rum**
- 1/2 teaspoon salt
- 4 cups powdered sugar
- 1/2 cup cream of coconut
- 3/4 cup sweetened, shredded coconut
- key lime slices
- Preheat the oven to 350 degrees. Grease and flour two 9" cake pans.
- Stir together the cake mix, eggs, oil, sour cream, key lime juice, milk, and zest in a mixing bowl. Beat on medium speed for 2 minutes.
- Divide the batter into the 2 prepared pans evenly. Bake for 26 minutes, or until a toothpick comes out clean. Place the pans on a cooling rack.
- Place the butter in a saucepan and heat over low heat until melted. Stir in the sugar and key lime juice. Bring to a boil. Reduce heat and simmer 1 minute. Remove from the heat and stir in the rum.
- Use a fork or skewer to poke holes all over the tops of the cakes in the pans. Drizzle the rum glaze evenly over both cakes. Let the cakes cool another 10 minutes in the pan.
- Place a piece of parchment paper over the tops of the cake and flip them out onto a plate. Place another plate on top of the cake and flip right side up. Let the cakes cool completely.
- Beat the butter and shortening until creamy. Add the coconut extract, rum, and salt and beat again.
- Slowly add the powdered sugar and cream of coconut until everything has been mixed in. Beat on high for 1-2 minutes, or until light and fluffy.
- Use a sharp knife to gently level the tops of each cake layer. Place one cake on serving plate. Spread half the frosting on top of the cake. Place the last cake layer on top, and spread the remaining frosting on top.
- Top the cake with the key lime slices and shredded coconut.