Saute onions and garlic in the butter or oil until about 6 minutes on medium heat until translucent. (if you are adding additional veggies, add them in this step increasing the oil or butter as needed)
Add the tomatoes, paste, herbs, salt, pepper, brown sugar, meatballs, and liquid.
Bring to low boil.
Cover and simmer on low for 15 minutes.
Add additional liquid, herbs, or salt & pepper and heat through.