[https://www.cooksillustrated.com/recipes/4142-fluffy-yellow-layer-cake?incode=MCSCD00L0&ref=new\_search\_experience\_1](https://www.cooksillustrated.com/recipes/4142-fluffy-yellow-layer-cake?incode=MCSCD00L0&ref=new_search_experience_1)

*Nonstick cooking spray can be used for greasing the pans (proceed with flouring as directed). Bring all ingredients to room temperature before beginning. Frost the cake with our Foolproof Chocolate Frosting (see related recipe) or your favorite topping.*

1. Adjust oven rack to middle position and heat oven to 350 degrees. Grease two 9-inch-wide by 2-inch-high round cake pans and line bottoms with parchment paper. Grease paper rounds, dust pans with flour, and knock out excess. Whisk flour, baking powder, baking soda, salt, and 1 1/2 cups sugar together in large bowl. In 4-cup liquid measuring cup or medium bowl, whisk together melted butter, buttermilk, oil, vanilla, and yolks.

2. In clean bowl of stand mixer fitted with whisk attachment, beat egg whites at medium-high speed until foamy, about 30 seconds. With machine running, gradually add remaining 1/4 cup sugar; continue to beat until stiff peaks just form, 30 to 60 seconds (whites should hold peak but mixture should appear moist). Transfer to bowl and set aside.

3. Add flour mixture to now-empty mixing bowl fitted with whisk attachment. With mixer running at low speed, gradually pour in butter mixture and mix until almost incorporated (a few streaks of dry flour will remain), about 15 seconds. Stop mixer and scrape whisk and sides of bowl. Return mixer to medium-low speed and beat until smooth and fully incorporated, 10 to 15 seconds.

4. Using rubber spatula, stir 1/3 of whites into batter to lighten, then add remaining whites and gently fold into batter until no white streaks remain. Divide batter evenly between prepared cake pans. Lightly tap pans against counter 2 or 3 times to dislodge any large air bubbles.

5. Bake until cake layers begin to pull away from sides of pans and toothpick inserted into center comes out clean, 20 to 22 minutes. Cool cakes in pans on wire rack for 10 minutes. Loosen cakes from sides of pans with small knife, then invert onto greased wire rack and peel off parchment. Invert cakes again and cool completely on rack, about 1 1/2 hours.

** For High-Altitude Baking** **Problem:** Chemically leavened cakes sink in the center. **Solutions:** Use less baking powder and/or baking soda. Increase the oven temperature and decrease the baking time. **Problem:** Egg-leavened cakes sink in the center. **Solutions:** Underwhip the whites and/or whole eggs. Increase the oven temperature and decrease the baking time. **Problem:** Cakes are dry and cottony. **Solution:** Use less sugar and/or add an extra egg. **Problem:** Cakes are greasy. **Solution:** Add an extra tablespoon or two of flour.

*This frosting may be made with milk, semisweet, or bittersweet chocolate. For our Fluffy Yellow Layer Cake (see related recipe), we prefer a frosting made with milk chocolate. Cool the chocolate to between 85 and 100 degrees before adding it to the butter mixture. The frosting can be made 3 hours in advance. For longer storage, refrigerate the frosting, covered, and let it stand at room temperature for 1 hour before using.*

*In food processor, process butter, sugar, cocoa, and salt until smooth, about 30 seconds, scraping sides of bowl as needed. Add corn syrup and vanilla and process until just combined, 5 to 10 seconds. Scrape sides of bowl, then add chocolate and pulse until smooth and creamy, 10 to 15 seconds. Frosting can be used immediately or held (see note).*

In food processor, process butter, sugar, cocoa, and salt until smooth, about 30 seconds, scraping sides of bowl as needed. Add corn syrup and vanilla and process until just combined, 5 to 10 seconds. Scrape sides of bowl, then add chocolate and pulse until smooth and creamy, 10 to 15 seconds. Frosting can be used immediately or held (see note).