In a saucepan, combine 2 cans of diced tomatoes and 1 can of crushed tomatoes.
Add 1 diced onion to the saucepan.
Mix in 3 tablespoons of basil and 2 pressed garlic cloves.
Bring the mixture to a boil over medium heat.
Once boiling, reduce the heat to low and let it simmer.
Simmer the sauce for 30 minutes, or until slightly reduced.