Preheat the oven to 325°F. Prepare two 9-inch round cake pans by lining them with parchment paper and spraying them with nonstick cooking spray with flour, or buttering and flouring them.
Whisk together the flour, baking powder, and salt in a medium bowl.
Microwave the milk and butter in a microwave-safe liquid measuring cup or bowl until the butter has melted. Stir in the vanilla. Wrap in foil to keep warm.
Whisk the whole eggs and sugar together on high speed until they are thick, pale, and very fluffy, about 4–5 minutes. The mixture should fall back like a ribbon that sits on the surface briefly before dissolving. This step is critical for the cake’s rise, as the whipped eggs provide structure and air.
Slowly whisk the warm milk and butter into the egg mixture until combined with the mixer on low speed. Fold in the flour mixture gently after removing the cake from the mixer. Be careful not to overmix.
Divide the batter evenly between the prepared cake pans as quickly as possible (a kitchen scale is helpful for even cakes).
Bake the cakes until an inserted toothpick comes out clean and the edges begin to pull away from the pan, approximately 23-28 minutes. Press gently on the top and it should spring back up. If the indentation remains, cook the cakes for a little longer. (Times can vary depending on your pans)
Cool the cakes completely in the pans. Upon cooling, the cakes can be wrapped in plastic wrap and stored at room temperature for up to 24 hours until assembling cake.