Toss tomatoes and onions (and optional garlic) with olive oil, 1 Tbs salt and 1 tsp freshly ground black pepper. Roast in the oven for 2 hours at 325°F.
Once the roasting vegetables have been removed, set the oven to broil. Place poblanos on aluminum foil under the broiler, allowing the skin to blacken, and rotating the peppers so that they are evenly roasted. When sufficiently blackened, remove from oven and wrap them with the foil so that they continue to steam. Once they have cooled, but before they are cold, remove the skin and seeds.
In a large non-reactive stockpot, mix the roasted tomato mixture and roasted poblanos with all remaining ingredients.
Bring to a full, rolling boil that cannot be stirred down and boil hard for 10 minutes.
Using standard, safe canning practices (For example, clean, glass jars, heated in the oven at 250°F) pour the salsa into pint jars. Alternately, pressure can at 10 lbs of pressure for 30 minutes.