Preheat oven to 400 degrees (roast).
Place the garlic cloves in the center of a 6"x6" square of foil with a few drizzles of water and close the packet up so there aren't any openings.
Place the garlic packet and the pepper with skin side up on a nonstick baking mat/pan and roast for 15 minutes.
While the peppers are roasting, place the onions in large nonstick skillet with 1/4 cup water. Cover and cook over medium heat until soft.
Add the chopped tomatoes and seasonings into the skillet, and cover again to cook down.
When the peppers and garlic are done, add them to the skillet (no need to chop the peppers).
Add the tomato puree and stir well to combine. Cover again and lower the heat to simmer for another 20 minutes. Turn heat off to let cool a bit.
Spoon the mixture from the skillet to a high-speed blender, and blend until desired consistency. Check for taste, and add salt and pepper if desired. You can also add a little sugar if your tomatoes were more on the acidic side.