Wash and prepare the tomatoes by skinning and seeding them.

In a large pot, heat olive oil over medium heat.

Add the chopped onion and minced garlic to the pot and cook until softened and fragrant.

Add the prepared tomatoes to the pot.

Bring the mixture to a boil, then reduce heat and simmer for approximately 60-70 minutes.

Continue to simmer, stirring occasionally, until the sauce has thickened and deepened in color.

Season with salt and pepper to taste during the last 15 minutes of cooking.

Puree the sauce with an immersion blender for a smoother texture (optional).

Let the sauce cool slightly before using or storing.