Preheat the oven to 400 degrees F.
Roast the tomatoes with ¼ cup of the olive oil, salt and pepper in a baking sheet for 45 minutes.
In a stockpot set over medium heat, sauté the onions and garlic with the remaining 2 tablespoons olive oil, half of the butter, and the Calabrese chile pepper for 10 minutes, until the onions start to brown. Add the canned tomatoes, basil, and vegetable stock. Add the oven-roasted tomatoes, including the liquid on the baking sheet. Bring to a boil and simmer uncovered for 40 minutes. Pass through a food mill fitted with the coarsest blade. Taste for seasonings. And the cheese and the other half of the butter let melt and serve hot.