Ingredients
1 cup (2 sticks) unsalted butter
1 3/4 cups sugar
4 large eggs plus 2 large egg yolks
1 tablespoon pure vanilla extract
3 cups cake flour (spooned and leveled)
1 tablespoon baking powder
1/2 teaspoon fine salt
1 1/2 cups buttermilk
Preparation
Bring cold ingredients to room temperature. Butter should be soft enough to hold a thumbprint but still keep its shape. In a large bowl, using an electric mixer, beat butter and sugar on high until light and fluffy, about 6 minutes.
Beat in 4 eggs plus 2 yolks, one at a time, until combined. Beat in vanilla extract.
In another large bowl, whisk together cake flour, baking powder, and salt. With mixer on low, add 1/3 the flour mixture to butter mixture, beating to combine.
Beat in 3/4 cup buttermilk, another 1/3 the flour mixture, another 3/4 cup buttermilk, and remaining flour mixture until just combined. Scrape down bowl as needed.
