In a nonstick pan over medium heat, warm the olive oil. Add the onion and cook, stirring often, until softened, about 4 minutes.
Add the garlic, chopped tomatoes, tomato sauce, water, tomato paste, and stir until combined. Adjust the heat to medium-low and simmer, stirring occasionally, for 20 minutes.
Serve immediately or store in an airtight container, tightly covered, and refrigerate for up to five days or freeze for up to two months.