Ingredients 2/3 cup butter, softened 1 3/4 cups white sugar 2 eggs 1 1/2 teaspoons vanilla extract 1 teaspoon grated grapefruit zest 1/2 cup fresh grapefruit juice 3/4 cup milk 3 cups sifted cake flour 2 1/2 teaspoons baking powder 1/2 teaspoon salt Directions Preheat oven to 350 degrees F (175 degrees C). Grease and flour two 9-inch pans. Sift together the flour, baking powder and salt. Set aside. In a large bowl, cream together the butter and sugar until light and fluffy. Beat in the eggs one at a time, then stir in the vanilla and grapefruit zest. Beat in the flour mixture alternately with the grapefruit juice and milk. Pour batter into prepared pans. Bake in the preheated oven for 25 to 30 minutes, or until a toothpick inserted into the center of the cakes comes out clean. Let cool in pan for 10 minutes, then turn out onto a wire rack and cool completely. Grapefruit Buttercream Ingredients: 1/2 cup butter, at room temperature 2 tablespoons of heavy cream or half-and-half 1 pound powdered sugar (about 3 to 4 cups) 1 1/2 cups grapefruit juice Directions: Begin by reducing the grapefruit juice. Place juice in a saucepan over medium-low heat. Allow to simmer for about 45 minutes, stirring occasionally, until juice thickens and becomes syrupy. Set aside to cool. In a large mixing bowl, cream butter, cream, and powdered sugar with an electric mixer. Continue whipping, and slowly add grapefruit syrup, one tablespoon at a time, until you reach desired flavor. I added about 3 tablespoons to mine, which resulted in a wonderfully tangy and fruity flavor.