For the Cake: 1 cup unsalted butter, softened 2 cups sugar 4 eggs 1 1/2 tsp. vanilla extract 1 1/2 tsp. finely grated grapefruit zest 3 cups cake flour 1 Tbs. baking powder 1/4 tsp. salt 1 cup milk For the frosting: 2 (8 oz.) packages cream cheese, softened 4 Tbs. unsalted butter, softened 2 tsp. freshly squeezed grapefruit juice 2 cups sifted confectioner’s sugar 2 large grapefruits, peeled and segmented 1 cup roasted pistachios, lightly crushed
Preheat oven to 350°F. Grease two nine-inch cake pans and line with a parchment round; grease and lightly flour top of parchment. In the bowl of an electric mixer fitted with a paddle attachment, cream the butter and sugar together on medium speed until light and fluffy, about three to four minutes. Add the eggs one at a time, beating well after each addition. Beat in the vanilla and zest. In a separate bowl, sift the flour with the baking powder and salt. With the machine running on low, alternate adding the flour mixture and the milk to the butter mixture, scraping down the sides of the bowl occasionally. Beat just until blended. Divide batter evenly between prepared pans. Bake about 25 minutes, rotating halfway through cooking, until tester inserted comes out clean. Cool on wire racks for 10 minutes. Loosen cake from sides of pan with a knife. Invert onto wire racks and remove parchment. Cool completely. To make the frosting, beat the cream cheese and butter until fluffy. Add the grapefruit juice and gradually blend in the sugar, making sure it’s thoroughly incorporated after each addition. To assemble the cake, invert the first layer onto cake platter. Spread with one-third of the frosting. Spread the grapefruit segments in a single layer, reserving some for garnish. Sprinkle with the crushed pistachios, pressing lightly to adhere. Spread an even thin coat of frosting over top of second layer and invert onto fruit/nut layer. Spread remaining frosting on top and sides of cake. Garnish top with remaining grapefruit segments.