Total time: 50 Minutes
1 tablespoon unsalted butter (softened, for greasing pan)
2 cups all-purpose flour (plus more for flouring pan)
¾ cup olive oil
½ cup granulated sugar
3 large navel oranges (divided)
1 large blood orange
1 ½ tablespoons chopped fresh rosemary (plus more sprigs for garnish)
2 large eggs
½ cup sour cream
2 teaspoons baking powder
½ teaspoon Diamond Crystal® Baking Salt
Powdered sugar (for garnish)
Preheat oven to 325°. Grease and flour a 9-inch round cake pan. Line with parchment paper and set aside.
Combine olive oil, sugar, zest of two oranges and rosemary in a large bowl using a hand mixer.
Beat on medium speed until combined. Add eggs, one at a time, until thick and fluffy. Add sour cream, and mix on low until combined, scraping down the sides as needed. Slowly add flour, baking powder and baking salt to wet ingredients until combined.
Slice blood orange and remaining navel orange into ⅛-inch slices using a mandolin or sharp knife. Layer orange slices into bottom of prepared pan, overlapping slightly. Top with batter and spread evenly into pan. Bake until golden-brown and a toothpick inserted in center comes out clean, about 30-35 minutes. Cool 10 minutes before inverting onto a wire rack to cool completely.
Garnish with rosemary sprigs. Dust with powdered sugar, and serve.