Don’t think about it—just do something nice for yourself. Making this cake is a step in the right direction. It’s beautiful, refreshing, and sweet—everything I try to tell myself and you should tell yourself, too. You’ll thank yourself later.
Topping
4tablespoons unsalted butter, plus more for the pan
1small to medium grapefruit
1navel orange
1Cara Cara or blood orange
½cup granulated sugar
¼cup light brown sugar
1tablespoon orange liqueur, optional
Cake
1¾cups all-purpose flour
1teaspoon baking powder
½teaspoon baking soda
½teaspoon salt
1stick (8 tablespoons) unsalted butter, softened
1cup granulated sugar
2large eggs
1teaspoon pure vanilla extract
1cup buttermilk
For the Topping
Preheat the oven to 350 degrees F. Generously butter a 9-inch round cake pan and line the bottom with parchment paper.
Use a fine grater to zest 1 teaspoon of zest from the grapefruit, navel orange, and blood orange (for a total of 1 tablespoon zest). Reserve the zest for the cake.
Cut the top and bottom off of each citrus and place them with a flat side on the cutting board. Then, following the curve of the fruit, use a sharp knife to cut off the peels and as much of the white pith as possible. Slice the fruit crosswise into ¼-inch-thick rounds; carefully remove any seeds.
Combine the butter and both sugars in a small saucepan and warm over medium-low heat until melted. Pour into the prepared cake pan and spread evenly. Top with the citrus rounds so they fit very snugly and are slightly overlapping (you may not use every slice). Drizzle with the orange liqueur, if using.
For the Cake
Whisk the flour, baking powder, baking soda, and salt together in a medium bowl. Put the butter, sugar, and reserved zest in another bowl and beat with an electric mixer on medium-high speed until light and fluffy, about 3 minutes. Add the eggs one at a time, beating after each addition. Beat in the vanilla. Add the flour mixture in 3 batches, alternating with the buttermilk, beginning and ending with the flour; mix until just combined.
Pour the cake batter over the citrus and bake until a wooden pick inserted into the center comes out clean, 50 to 60 minutes. Run a sharp knife around the edge of the cake and let it cool for 15 minutes, then carefully invert it onto a platter, replacing any citrus that may have stuck to the pan. Serve slightly warm or at room temperature.