What’s the best way to get a two-layer cake to cook evenly? We baked our Classic White Layer Cake in three placements: side by side on one rack; on two racks with one pan directly above the other; and on two racks with one pan on the top left of the oven and the other on the lower right. Only the cakes on the same rack baked evenly.
The reason is convection—the hot air currents moving around the oven. In bottom-heating ovens, when cakes are stacked, the bottom one acts as a barrier, creating hot air currents that flow up and over the top cake. The result is an overcooked top cake and an undercooked bottom cake. Results are also uneven in rear-heating ovens or those with top and bottom elements. But when cakes are baked side by side, hot air circulates evenly no matter how your oven heats. If you need to cook three cakes at a time, place two on the bottom rack, spaced apart, and one on the rack above and in between the other two. Move the cakes twice during cooking so that each cake spends an equal amount of time in each position.