Butter the bottom and sides of 3 6" round cake pan, Line the bottom with parchment paper and butter the paper. Coat the bottom and sides with flour.
Preheat your oven to 350℉.
In a bowl combine the all purpose flour, cake flour, baking powder and salt. Set aside.
Combine the milk and butter and heat until the butter is melted and the mixture reaches a temperature of 140℉.
In the bowl of an electric stand mixer, or a large bowl if using a hand mixer, place the sugar and lemon zest and massage together using your fingertips. Add the eggs. and using the whisk attachment beat on high speed for 3-4 minutes until lighter in color and about tripled in volume.
Sift the dry ingredients into the egg/sugar mixture and beat on low until everything is combined.
With the mixer running on low spead, gradually add the hot milk/butter and mix until combined.
Scrape the bottom and sides with a rubber spatula to insure that all the ingredients are combined.
Divide the batter evenly into the 3 prepared pan and bake for 15-18 minutes or until the top is a light golden brown and the top springs back when gently pressed.
Remove the cake from the oven and place the pan on a rack to cool.
Next, remove the cake from the pan, remove the parchment paper from the bottom and place on a rack to cook completely.