Roast the Tomatoes
Preheat the oven to 400° F.
Toss together the tomatoes, ¼ cup olive oil, salt, and pepper.
Spread the tomatoes in 1 layer on a baking sheet and roast for 45 minutes
Make the Sauce
In an 8-quart stockpot over medium heat, saute the onions and garlic with 2 tablespoons of olive oil, the butter, and red pepper flakes for 10 minutes, until the onions start to brown.
Add the tomatoes, basil, thyme, and chicken stock.
Add the oven-roasted tomatoes, including the liquid on the baking sheet. Bring to a boil and simmer uncovered for 40 minutes. (If making a sauce, let the soup reduce down until it's thicker like a sauce would be)
Pass through a food mill fitted with the coarsest blade. Taste for seasonings.
Serve hot or cold.