Place a 10 or 12-inch skillet over medium-high heat and add the olive oil or butter.
Once hot, add the chopped onion and cook, stirring occasionally, until it has softened, about 2 to 3 minutes.
Add the drained, chopped tomatoes to the skillet, along with a generous sprinkling of salt and pepper.
Cook, stirring every few minutes, allowing the tomatoes to break down and the sauce to thicken and come together. This should take 10 to 15 minutes.
Taste the sauce and adjust the seasoning with more salt or pepper if needed.
Serve immediately tossed with your favorite pasta, garnished with cheese or fresh herbs if you like. Leftover sauce can be refrigerated for up to 4 days.
Sauté 2-3 minced garlic cloves with the onion for an extra layer of aromatic flavor.
