Salsa pizzaiola is the traditional tomato sauce for pizzas. It's very similar to salsa di pomodori, and it's quite possible to modify salsa di pomodori to make a passable substitute for salsa pizzaiola. I'll show both ways here.

From scratch

quantity		ingredient	Step
60 ml		Olive oil	1
200 g		Onion	1
20 g		Garlic	1
800 ml		Tinned tomatoes	2
150 g		Tomato concentrate paste	3
30 g		Fresh oregano or	3
10 g		Dried oregano	3
5 g		Basil	3
1		Bay leaf	3
20 g		Sugar	3
10 g		Salt	3
		Black pepper	3

Procedure

Start at least 60 minutes before use.

1. Finely chop onion and garlic and fry in the olive oil until glassy but not browned.
2. Finely chop the tomatoes in a mixer.
3. Add the other ingredients to the onions, bring to the boil and simmer for 40 minutes.
4. Before use, remove the bay leaf.

From salsa di pomodori

Warm 250 ml of salsa di pomodori in a saucepan. Add 10 g of chopped garlic and 15 g fresh or 1 g dried oregano. Keep warm for 10 minutes.