Heat the oil in a large skillet over medium-high heat. Add the onions, garlic, salt, and white pepper. Cook, stirring often, until the onions are softened, about 4 minutes. Add the tomatoes and basil. Cook,stirring often, for 5 minutes. Add the stock and black pepper. Reduce the heat to medium-low and simmer for 2 minutes.
Add the sugar to balance the acidity if needed, and cook for 1 minute. This keeps for five days, refrigerated in an airtight container.
Yield: about 3 cups