Preheat oven to 350 Deg F. Line the bottom or three 8” round cake pans with parchment paper.
In a small bowl sift together the flour and cocoa powder.
In another small bowl melt the butter and allow it to cool to room temperature as the eggs and sugar mix.
In a stand mixer with the whisk attachment, mix the eggs and sugar together on high for 5-7 minutes until thick and pale and tripled in volume. Add in the vanilla and salt and whip another minute.
Fold in the flour mixture in two portions into the egg mixture, being careful not to deflate the egg mixture. Take out a cup of the mixture and combine with the melted butter, then add back into the rest of the batter and fold in a few more times. A few streaks of flour is ok, you really don’t want the batter to deflate too much.
Divide amongst the prepared pans then bake for 20-24 minutes or until the cakes are puffed and a toothpick inserted in the middle comes out clean. Let cool completely in pans, then carefully run a knife around the edges and invert to a cooling rack, or wrap in plastic wrap and chill until ready to use.