A 3 ingredient sauce is perfect for weeknights or weekends when you have lots of running around to do or a laundry pile that is waist high. You can get this sauce started (ie. throw 3 things in a saucepan) in less than 5 minutes and then you're basically free to do anything that needs to be done for at least the next 45 minutes.
As for the flavor, it's simple, smooth, and mellow. The tomatoes are the star player in this sauce so it's important to go with a good brand of canned tomatoes. I've had luck with Trader Joe's brand as well as San Marzano. Once I tried it with Von's store brand and I wasn't as happy with the results, so keep that in mind. Also something to note, almost every time I see this online people include salt on the ingredient list (as will I) but they all say they didn't need it. This was true with me too, no extra salt, hence the title 3 Ingredient and not 4 Ingredient. I did however top mine with lots of fresh Parmesan before eating (not pictured) because that's how I roll. Some may disagree that this sauce needs the cheese, but to me all sauce needs it.
Ingredients
28 ounces whole peeled tomatoes from a can *
5 Tbsp butter
1 medium-sized yellow onion, peeled and halved
Salt to taste, though I have never needed it
* Once I accidentally bought a can of whole tomatoes with basil, and it also did well. Some would say the basil takes away from the simplicity of the sauce but it tasted good, so it can't be "wrong".
Directions
Place the tomatoes, onion, and butter in a saucepan over medium heat and bring to a simmer. Reduce heat to low and simmer for at least 45 minutes, occasionally stirring and using the spoon to begin to break down tomatoes. At the end of the simmer remove the pan from the heat, discard the onion, and use a wooden spoon to crush the tomatoes on the side of the pan. Season with salt only if needed.
Serve with pasta shape of your choice and grated Parmesan cheese for topping. I also served with a side of broccoli.
Source: Smitten Kitchen