In a large bowl, whisk together eggs, milk, vanilla extract, salt and cinnamon. Heat a large skillet or griddle over medium to medium-low heat. Gently dip each piece of angel food cake into the egg mixture, fully submerging it and covering all the sides. Make sure to let most of the egg drip off. Place a bit of butter in the skillet/griddle, then place cake on it and cook until golden, about 2-3 minutes per side. The only additional step here is you want to fry each side, then turn it on it’s “back” and get that thick third end of the cake. Repeat with remaining slices, adding a bit of butter each time.