Of course you can have more than one favorite food, but singular/plural has to be written accordingly.
What is your favorite food? Pizza.
What are your favorite foods? Pizza and burgers.
What food do you like the most? Pizza.
What foods do you like the most? Pizza and burgers.
Favorites often follow more specific categories, like favorite chocolate bar or favorite fruit. So even if you want to say you can only have one favorite food, in fact you can have several.
At least for foods, favorite and like the most mean roughly the same thing. Other contexts may be different.
In case it is not obvious, it is favorite in AmE.