Cut dough into 8 slices.
Cut the block of mozzarella cheese into 8 cubes.
Flatten a piece of dough. Top with a slice of pepperoni, mozzarella cheese and another slice of pepperoni. Continue with all of the dough pieces.
Mix together hot water and baking soda. Dip filled dough balls into the baking soda mixture. Place them in a greased 9-inch cast iron skillet or oven-safe pan.
Bake at 400 degrees for 12-17 minutes, until golden brown.
Brush with melted butter and sprinkle with salt.