1¾ c (3½ sticks) unsalted butter, browned and at room temperature (directions below)
2⅔ c (530 g) granulated sugar
9 egg whites, at room temperature
4-1/2 cups (570 g) all-purpose flour
2 tablespoons (22 g) baking powder
1 teaspoon (6 g) salt
2 cups buttermilk, at room temperature
3 tsp vanilla extract
½ tsp almond extract
Instructions
Preheat oven to 350 degrees
Butter 2 (or 4, if you have them) 6 inch cake pans, line the bottom with parchment paper and dust with flour, tapping out the excess.
Place butter in a heavy-bottomed sauce pan and melt over low-medium heat, stirring and scraping the bottom of the pan occasionally. When milk solids begin browning and the butter smells nutty transfer it to a heat proof bowl and either place in the fridge or in an ice bath until cooled and solidifying.
Place butter and sugar in the bowl of an electric mixer and beat on high speed until light and fluffy, about 5 minutes. Reduce speed to medium and slowly add the egg whites, mixing until incorporated.
Sift the remaining dry ingredients together. Add vanilla and almond extracts to buttermilk.
Alternate adding wet and dry ingredients to the mixer, beginning and ending with dry ingredients and mixing just until combined or finishing by hand.
Divide the batter evenly between the prepared pans, weighing if possible (should be about 506 g of batter per pan). Level out the batter with a small offset spatula or the back of a spoon.
Bake for 20 minutes, then rotate the pans in the oven. Check every few minutes until a toothpick inserted in the center of the cake comes out clean.
Place the pans on a cooling rack for 10 minutes, then run a knife around the edges of the pan and gently turn the cake out onto a cooking rack. Allow to cool completely.
Wash and repeat with the remaining batter if necessary.
Recipe by oh honey bakes at https://ohhoneybakes.com/brown-butter-cake-with-grapefruit-curd-and-rosemary-brown-sugar-buttercream/