Blend the tomatoes into a chunky puree using a food processor or mill.
In a medium saucepan over medium-low heat, combine 1 tablespoon of olive oil with 2 tablespoons of butter.
Once melted, add your minced garlic, oregano, and salt. If you want a bit of a spicy kick, add a dash of red pepper flakes.
Stir continuously for about 3 minutes.
Add the tomatoes you've set aside, along with a tablespoon of sugar, directly to the butter mixture. Peel and slice the white onion in half and add it in there too.
Once it simmers, reduce the heat of your stovetop to the lowest setting. Leave it for about an hour and stir occasionally.
Discard the onion once the hour is up. Let it cool for a while before using it on your pizza.