Preheat oven to 350 degrees F.
Prepare one 9 inch pan with baking spray or butter.
Separate Eggs. Make sure you do each egg in an individual bowl. Break egg into bowl. Lift out yolk. Save in separate bowl. Pour this egg white into the bowl you'll be mixing. Do this with each egg white just in case one of the yolks breaks.
Beat until soft peaks form and the egg whites resemble marshmallow cream.
In meantime, melt chocolate by placing stainless steel bowl over a saucepan that has two inches water at a simmer.
Once egg whites are mixed, transfer to a bowl. Clean mixer.
Mix hazelnut flour, coconut flour, salt in mixing bowl. Set aside.
Cream butter and swerve (or sugar) in mixer until smooth.
Add egg yolks and mix well.
Add melted chocolate.
Add in dry ingredients.
Fold in egg whites.
Use an offset spatula to smooth out batter.
Bake in center of oven for 30 minutes. Test cake with cake tester. It should come out clean.
Cool completely before cutting.