Heat the oil in a large nonreactive skillet over high heat. Add the onions, garlic, salt, and white pepper and sautČ for 3 minutes. Add the tomatoes and basil and cook, stirring occasionally, for 3 minutes.
Stir in the stock and the black pepper and simmer for 2 minutes. Fold in the butter and as soon as it begins to melt, remove the skillet from the heat. Continue to stir in the butter until itís thoroughly incorporated. Serve immediately or prepare without the butter. Store, refrigerated, in an airtight container for up to 2 days. Reheat in a saucepan over low heat. When the sauce is at a simmer, fold in the butter and proceed.
Yield: about 2 cups