For the obmré citrus topping:
- ¼ cup granulated sugar
- 1 tablespoon water
- 2 tablespoons unsalted butter
- 1 Blood orange
- 1 Cara Cara orange (can sub grapefruit)
- 1 Navel orange
- 1 lemon (Meyer or regular)
For the cake:
- 1 ½ cups all-purpose flour
- 1 teaspoon baking powder
- ½ teaspoon baking soda
- ¼ teaspoon salt
- 1 cup granulated sugar
- Zest of 1 orange & 1 lemon (about 2 tablespoons zest)
- 8 tablespoons (1 stick) unsalted butter, room temperature
- 2 large eggs, room temperature
- ¾ cup buttermilk, room temperature
- Preheat the oven to 350F. Line an 8-inch baking pan with parchment so that it covers the bottom and sides. Set aside.
- Add the sugar, water and butter to a microwave safe bowl and heat for 30-45 seconds until butter and sugar are melted. You may need to stir to fully dissolve the sugar. Pour the mixture into the bottom of the lined pan.
- With the skin still on, use a paring knife to slice citrus to about ¼-inch thickness. Carefully cut the skin off of each slice, removing as much of the pith (white part) as possible while keeping your slices in-tact.
- Arrange the citrus in an ombré pattern in the prepared pan. You may need to cut the slices into halves and quarters in order to fill all of the open space. Make sure to tuck them in tightly.
- In a medium bowl, whisk together the flour, baking powder, baking soda and salt. Set aside.
- In a separate bowl, add the sugar and citrus zest and use your fingers to massage the zest into the sugar. This will release the oils and make the citrus more fragrant and flavorful.
- Add the room temperature butter and citrus-infused sugar to the bowl of a stand mixer fitted with paddle attachment and beat until light & fluffy, about 5 minutes. Add the eggs one at a time and beat until thoroughly mixed.
- Alternate adding the flour and buttermilk, starting and ending with the flour, and beat until just incorporated, being careful not to overmix. The batter will be fairly thick and fluffy.
- Spoon the batter over the citrus and then use a spatula to gently spread it evenly over the fruit.
- Bake for approximately 35 minutes, or until a toothpick inserted into the center comes out clean. Let cool completely in the pan (3-4 hours minimum) before turning the cake out onto a serving dish. Enjoy!