Put everything together: In an 8-quart stockpot heat one tablespoon of olive oil and one tablespoon of butter over medium heat, sauté the onions and red pepper flakes for 10 minutes, until the onions start to brown and fond begins to develop on the bottom of the pan. Add the red wine vinegar to deglaze the pan. Then add the canned tomatoes, basil, thyme, and chicken stock. Add the oven-roasted tomato/garlic/bell pepper mixture (including the liquid on the baking sheet) and parmesean rind (if using) to the pot. Bring to a boil, lower heat to medium-low and simmer uncovered for 40 minutes.