Upside-Down Blood Orange Cake

Ingredients

• 270 grams unsalted butter (2 sticks plus 3 tablespoons), at room temperature
• 130 grams light brown sugar (about 2/3 cup)
• 2 teaspoons fresh lemon juice
• 2 medium-sized blood oranges
• 122 grams fine cornmeal (about 1 cup)
• 65 grams all-purpose flour (about 1/2 cup)
• 8 grams baking powder (about 1 1/2 teaspoons)
• 2 grams fine sea salt (about 1/2 teaspoon)
• 200 grams granulated sugar (about 1 cup)
• 4 large eggs, at room temperature
• ⅓ cup sour cream
• 2 teaspoons vanilla extract

Directions

1. Heat oven to 350 degrees. Grease a 9-inch round cake pan.
2. In a small saucepan over medium heat, melt 3 tablespoons (45 grams) butter. Add the brown sugar and lemon juice; stir until sugar melts, about 3 minutes. Scrape mixture into bottom of prepared pan.
3. Grate 1/2 teaspoon zest from one of the oranges, then slice off the tops and bottoms of both oranges. Place oranges on a clean, flat surface, and slice away the rind and pith, top to bottom, following the curve of the fruit. Slice each orange crosswise into 1/4-inch-thick wheels; discard any seeds. Arrange orange wheels on top of brown sugar mixture in a single, tight layer.
4. In a large bowl, whisk together orange zest, cornmeal, flour, baking powder and salt. In a separate bowl, cream together remaining 2 sticks (225 grams) butter with granulated sugar. Beat in eggs, one a time, then beat in sour cream and vanilla. Fold in the dry mixture by hand.
5. Scrape batter into pan over oranges. Transfer to oven and bake until cake is golden brown and a toothpick inserted in the center emerges clean, 40 to 50 minutes. Cool cake in pan 10 minutes, then run a knife along pan’s edges to loosen it; invert onto a platter and cool completely before serving.