Grapefruit buttercream cake

Grapefruit Cake

1/2 cup granulated sugar
Zest of 1 grapefruit
2 large eggs
1 cup plain non-fat Greek yogurt
1/3 cup light olive oil
1 teaspoon vanilla extract
1/3 cup + 2 tablespoons freshly squeezed grapefruit juice (about 1 grapefruit)
2 cups all-purpose flour
1 tablespoon baking powder
1/4 teaspoon salt

Preheat oven to 350 degrees F (180 degrees C). Grease 2 8-inch cake pans.

In a large mixing bowl, mix together sugar and grapefruit zest with your fingers until fragrant. Beat in eggs one at a time, mixing well between each addition. Mix in yogurt, olive oil, vanilla extract, and 2 tablespoon grapefruit juice (reserve 1/3 cup for later). Stir in flour, baking powder, and salt.

Divide batter evenly between cake pans and bake for 35-45 minutes, or until a toothpick inserted into the center comes out clean. Using a pastry brush, brush remaining 1/3 cup grapefruit juice on top on the cake layers, allowing the juice to soak into the cake. Allow to cool to room temperature.

Grapefruit Buttercream
3/4 cup freshly squeezed grapefruit juice
8 tablespoons (1 stick) butter, room temperature
Zest of 1 grapefruit
4 cups powdered sugar
Heavy cream

In a small saucepan, bring grapefruit juice to a boil and simmer until it reduces and thickens to about 1/4 cup. Cool to room temperature.

In a large mixing bowl, beat together butter and grapefruit zest until smooth. Mix in thickened grapefruit juice. Gradually add powdered sugar until incorporated and smooth. Because the thickened grapefruit juice will vary in amount, add heavy cream one tablespoon at a time until desired consistency is achieved.

Original recipe found here.