Answer:
I'm a type of pizza that is folded in half before cooking to contain a filling
I am round as a bowl, deep as a tub, but all the world's water couldn't fill me up.
What goes in the water red, and comes out black?
What is never used unless it's in a tight place?
What is bought by the yard by is worn by the foot?
I fly to any foreign parts assisted by my spreading wings. My body holds an hundred hearts Nay I will tell you stranger things when I am not in haste I ride and then I mend my pace anon.