Preheat Oven to 350˚F. Line bottoms of two 9″ cake pans with parchment paper (do not grease the sides).
In the bowl of an electric stand mixer fitted with whisk attachment (this is the one I have), beat 6 large eggs for 1 minute on high speed. With the mixer on, gradually add 1 cup sugar and continue beating 8-10 minutes until thick and fluffy.
Whisk together 1 cup flour and ½ tsp baking powder then sift this mixture into fluffy egg mixture one third at a time. Fold with a spatula with each addition just until incorporated. Scrape spatula from the bottom to catch any pockets of flour and stop mixing when no streaks of flour remain. Do not over-mix or you will deflate the batter.
Divide evenly between prepared cake pans (it helps if you have a kitchen scale to weight the pans). Bake at 350˚F for 23-28 minutes (my oven took 25 min), or until top is golden brown. Remove from pan by sliding a thin spatula (here’s the one I love for cakes) around the edges then transfer to a wire rack and remove parchment backing.
Cool cakes to room temperature then slice layers equally in half with a serrated knife.
When no streaks of flour remain in the dough, fold a few extra times to ensure you aren’t missing pockets of flour at the bottom
Bake the cake layers right after folding in the flour – they should not sit too long
Always use a conventional oven setting (not a convection/fan setting)
An electric hand mixer will take 2-4 minutes longer to beat the eggs
Bake in the center of the oven
Place cake in a fully pre-heated oven
Do not open the oven door to check on the cake until towards the end
Let the cake cool in a room without any outdoor draft which can make it seem eggy