Drain oil from tuna and add to a large mixing bowl. Finely dice red onion and celery branches and add to the bowl with the tuna. Add the mayonnaise, salt and pepper to the bowl and combine ingredients.
Bake the Parmesan Lemon Waffle Fries according to the package instructions. Keeping the oven on, remove the fries from the oven and top each fry with a spoonful of the tuna mixture.
Place a slice of cheddar cheese on top each fry and return to the oven until the cheese melts. Remove from the oven and top each fry with a slice of roma tomato. Serve immediately.