You could buy pizza sauce but i tried making my own. Heat some oil and fry onion and garlic then cook through the tomato puree before adding chopped tomatoes and dried herbs. Bring to boil then simmer gently for 30 mins. Season with salt and pepper. Sieve, pushing as much sauce through, and scrapping back of sieve. Bring sieved sauce back to heat gently and set aside for topping. Alternatively blitz in food processor.