Step 1 Heat the olive oil in a medium saucepan over medium-high heat. Add the onion and the garlic and cook, stirring constantly, until they're very fragrant, about 1 to 2 minutes. Add the tomatoes and bring to a boil. Reduce the heat to medium-low and simmer the sauce until the tomatoes have softened and the sauce has thickened slightly, about 20 minutes. Stir in the thyme, and salt and pepper to taste. Cook another 2 to 3 minutes. Taste the sauce and add the sugar if the sauce is slightly bitter. Add the crushed red pepper, if you want, for a little more punch. Makes 2 1/2 cups.