makes one 10-inch cake or two 7-inch cakes
- 1 small (325 g) grapefruit
- 2½ cups (500 g) sugar
- 3 cups (375 g) all-purpose flour
- 2 tspn baking powder
- 1 tspn baking soda
- 1 tspn salt
- 2–3 Tbspn chopped fresh rosemary (see note)
- 4 eggs, at room temperature
- 6 Tbspn (81 g) extra virgin olive oil
- confectioners’ sugar
- Trim a small amount from the bottom and top of the grapefruit, just enough to reveal the flesh. In a small pot, cover the grapefruit with water and bring to a boil. Cook for about 1 minute and drain, discarding the water. Repeat the boiling, cooking, and draining twice more.
- Combine the blanched grapefruit, 1 cup (200 g) sugar, and 3 cups (690 g) water in the small pot over medium heat. Cook for about 20 to 30 minutes, stirring frequently, until the sugar dissolves and the grapefruit rind is fork-tender. Remove the grapefruit from the cooking liquid, saving the liquid for later. Let both cool to room temperature.
- Preheat oven to 180° C. Grease and flour one 10-inch round cake pan or two 7-inch round cake pans and set aside.
- In a bowl, whisk to combine the flour, baking powder, baking soda, salt, and chopped rosemary. Set aside.
- Cut the grapefruit in half and scoop the flesh into a food processor. Scrape a majority of the pith from the rind and discard the pith. Add the grapefruit rind to the food processor. Add the eggs and pulse to combine, until the grapefruit is a chunky purée. Add the remaining 1½ cups (300 g) sugar and olive oil to the food processor and pulse to combine well. Add the flour mixture in two additions, pulsing briefly to incorporate the flour. Do not overmix.
- Transfer the batter to the prepared pan(s). Bake for 40 to 50 minutes, until a toothpick inserted in the center of the cake comes out clean and the edges and top are just turning golden brown. Remove from oven and place on a wire rack.
- Brush a small amount of the reserved grapefruit cooking liquid on top of the cake. Let cool for about 10 to 15 minutes before removing the cake from the pan and letting cool completely.
- Serve when cool, with a generous amount of powdered sugar.
Note: adjust the amount of rosemary dependent on the potency of the herb that you have on hand. For a cake with lighter rosemary flavor, go with 2 Tbspn. For something more robust, go with 3 Tbspn.