Ingredients:

For the Base:
4 hamburger patties

For the Topping:
2 tomatoes drained (canned)
1 generous teaspoon tomato puree
1 small dash olive oil
2 pinches dried basil
1 pinch ground black pepper
1 tiny pinch salt
mozzarella cheese sliced, enough to cover 4 patties or about a handful of grated dry mozzarella

For the Rolls:
2 fresh bread rolls, about the same size as the patties
butter

Methods:

Chop the tomatoes into small cubes, add the puree, basil, pepper, salt, olive oil and mix thoroughly.

The patties should preferably be broiled under a grill or cooked on a Weber-like barbecue with the lid on.
Grill/broil the patties until half cooked and flip them over. Barbecue:- immediately spoon the sauce onto the patties, cover liberally with cheese and put the lid on the barbecue. Oven/Broiler:- wait a minute or two after turning the patties before you add the toppings. The burgers are ready when the cheese has melted.

Split the rolls and toast the cut surfaces lightly (under grill, on barbecue or in a dry pan) just before the patties are done. Spread a little butter on the toasted surfaces, add the patty and enjoy a great tasting Pizza Burger.
You could use 4 rolls and top the patty with the other half but I prefer them this way.