Step 1

Heat the oven to 350°F with a rack in the middle position. Mist two 8- or 9-inch round cake pans with cooking spray. Line the bottoms with rounds of kitchen parchment, then mist the parchment. Dust the pans with flour, then knock out the excess.

Step 2

In a large bowl, whisk together the flour, baking powder, baking soda and salt. In a blender, combine the buttermilk, butter, whole eggs and egg yolks, oil, vanilla and sugar. Blend on high just until combined, about 15 seconds, scraping the jar about halfway through to make sure the sugar has not clumped on the sides; do not overblend. Pour the wet ingredients into the dry ingredients, then whisk just until evenly moistened. Divide the batter evenly among the prepared pans, then rap each pan 2 or 3 times on the counter to remove any air bubbles.

Step 3

Place the pans in the oven, evenly spaced on the rack. Bake until golden brown and a toothpick inserted in the centers comes out clean, 22 to 25 minutes. Cool in the pans on a wire rack for 15 minutes. Run a paring knife around the edge of each cake to loosen. Invert the onto the rack, lift off the pan and peel off the parchment. Cool completely, about 1 hour.