In a large Dutch oven or saucepan, warm the olive oil over medium-low heat (use just enough to coat the bottom of the pan). Add the onions, garlic and sugar, along with a pinch of salt. Cook for 3-5 minutes until translucent, stirring periodically, then add the tomato paste. Cook for another 2-3 minutes, stirring frequently, then add the strained tomatoes and oregano.
Stir, then cover and simmer on low/medium-low for at least 45 minutes or up to 1 1/2 hours. The longer the sauce cooks, the better the flavor of the sauce will be.
Remove from the heat, and add the oregano, salt, pepper and crushed red pepper if using. Taste and add additional seasoning if needed. If you want a smoother consistency, you can puree the sauce in a blender.
Store in an airtight container in the refrigerator for up to 4 days. You can also freeze the sauce for 3-4 months.
You can swap out the granulated sugar for finely chopped dates, if you prefer to avoid processed sugars. They will dissolve into nothing as the sauce cooks down. Chop 2 medium dates finely, and add along with the onions and garlic.Oregano is a great all-purpose sauce ingredient that will translate will into a pizza sauce. If you know this sauce will be used for pasta, try adding in some chopped fresh basil as well! I recommend adding 1/4 cup, tasting, and then adding more if you think the sauce needs it. You can also use either oregano or basil as a garnish when you serve. These herbs loose some of their flavor when they cook.