Yellow Layer Cake

Adjust oven rack to lower-middle position and heat oven to 350 degrees. Grease two 9-inch or three 8-inch round cake pans, line with parchment paper, grease parchment, and flour pans. Whisk flour, 1 1/4 cups sugar, baking powder, baking soda, and salt together in large bowl. Whisk buttermilk, egg yolks, melted butter, oil, and vanilla together in separate bowl. Add buttermilk mixture to flour mixture and whisk until just combined.

Using stand mixer fitted with whisk attachment, whip egg whites and cream of tartar on medium-low speed until foamy, about 1 minute. Increase speed to medium-high and whip whites to soft, billowy mounds, about 1 minute. Gradually add remaining 1/4 cup sugar and whip until glossy, stiff peaks form, 2 to 3 minutes.

Whisk one-third of whites into batter. Using rubber spatula, gently fold remaining whites into batter until no white streaks remain. Divide batter evenly among prepared pans, smooth tops, and gently tap pans on counter to release air bubbles.

Bake until tops are light golden and toothpick inserted in center comes out clean, 18 to 22 minutes (for 8-inch pans) or 20 to 25 minutes (for 9-inch pans), rotating pans halfway through baking. Let cakes cool in pans for 15 minutes. Remove cakes from pans, discard parchment, and let cool completely on wire rack, about 2 hours.