I prefer to use an uncooked tomato sauce on pizza. The sauce will cook with the rest of the topping.
To make a simple tomato sauce, use a hand mixer, potato masher or, better still, your hands, to mash a can of peeled tomatoes into a sauce. Drain some of the the juice.
Make sure to try and get the right consistency – neither too thick, nor too watery. You want your sauce to spread easily on the pizza dough, without making it soggy. If you like a lot of sauce on your pizza, make it a little thicker.