On Sundays he makes pizza.
This could be he makes pizzas (count noun) or he makes pizza (mass noun) - both are in use. He makes a pizza is possible, but would imply that he only ever makes one pizza.
Sometimes he fries chicken ...
Exactly the same as "pizza": "chickens" or "a chicken" would both be possible; except that when you refer to chickens as count nouns ("chickens" or "a chicken") it tends to mean whole chickens, rather than just some chicken-meat.
... or Chinese food.
"Food" is always a mass noun (except, like many mass nouns, when it means "kinds of food").
In all the above, you have not yet introduced the food in question to the discourse, so "the" is not appropriate.
She cuts the vegetables. She tosses the salad.
Even though the vegetables and the salad have not yet been explicitly mentioned, the prior reference to the pizza or chicken has brought the meal into the discourse, so "the" may be used to refer to parts of the meal. It would also be possible to use indefinite articles here:
She cuts vegetables and tosses a salad.