Easy Tomato Onion Sauce

This easy tomato onion sauce is made with just 3 ingredients – onions, tomatoes and olive oil. The onions are cooked until they are tender and sweet, then simmered in the tomatoes. It’s delicious as a pasta sauce, but I also love adding it to many other recipes.

Easy tomato onion sauce made with just 3 ingredients, tomatoes, onions and olive oil.

Made with fresh tomatoes and plenty of sweet onions, this easy tomato sauce is absolutely delicious. There is such a depth of flavor when you simmer the tomatoes for a few hours.
Cooking the onions first in olive oil until they are sweet and tender gives the tomato sauce a natural sweetness. This tomato sauce has a lovely clean flavor but it gets really concentrated and has a rich and deep flavor after it bubbles away on the stove.

Use this as a pasta sauce, served simply with some fresh herbs and grated cheese, or add some meatballs or sausage to make it more hearty. I also love to use it in many other recipes, like stuffed peppers, lasagna, cabbage rolls or Borsch.

Video of how to make easy tomato sauce:


fresh tomatoes – using fresh tomatoes instead of canned is the secret to this tomato sauce. The flavor is significantly different. The tomatoes are much sweeter and less acidic. Most canned tomatoes have added lemon juice or vinegar. If you usually get heartburn from tomato sauce, it is very likely that this one won’t give you heartburn, because it isn’t as acidic.

Of course, you can use canned tomatoes if you don’t have fresh tomatoes.

onions – don’t be alarmed at the amount of onions used. They will add so much delicious aromatic flavor as well as a sweetness that is intensified as the onions become tender and golden.

olive oil – you can also use avocado or sunflower oil.

salt, ground black pepper, to taste

fresh herbs, such as parsley and basil, optional, as a garnish

How To Make Easy Tomato Onion Sauce:

  1. Prep the tomatoes. I highly recommend peeling and seeding the tomatoes first, but that is completely up to you. You can simply cut out the tomato core and leave the seeds and tomato skin on. I like the tomato sauce to be really smooth, so I remove the skin and the seeds.
  2. How to peel the tomatoes:
    • Bring a pot of water to a boil. Meanwhile, cut an X on the top and bottom of each tomato with a paring knife. Place the tomatoes into the boiling water for 30 seconds, remove the tomatoes from the boiling water and plunge into a bowl of cold ice water. The skin will come right off very easily.
    • Remove the seeds from the tomatoes. I like to drain them over a fine mesh sieve, save the tomato juice and add it into the pot along with the tomatoes.
  3. Slice the onions into thin half circles.
  4. Then, saute the onions. In a large, heavy bottomed pot, (about 8 quarts), heat the oil until shimmering, then add the onions, seasoning with salt and pepper to taste. Cook, until the onions are soft and starting to get golden, about 15 minutes.
  5. Add the tomatoes and the tomato juice to the onions, season with salt and pepper to taste. Bring it to a boil, then reduce to a simmer and cook for about 2 hours, covered, at a low simmer, until the tomatoes are soft and the sauce has reduced.
  6. Puree the sauce in batches using a blender or use an immersion blender* right in the pot until it is the consistency that you like. You can leave it chunky or make it really smooth.
  7. To store, refrigerate the sauce for about a week or freeze for up to 6 months.
Easy Tomato Sauce tutorial using fresh tomatoes and onions.

Serving the Easy Tomato Sauce

My absolute favorite way to serve this sauce is simply with some fresh herbs, angel hair pasta or spaghetti and then some finely grated cheese on top. Simplicity at its finest!

We also love it with some juicy beef meatballs. I use this recipe, just omit the sauce and use this one instead.

Helpful Tips and Frequently Asked Questions

Can you use canned tomatoes instead of fresh tomatoes?

Yes, absolutely! However, since the canned tomatoes usually have a decent amount of citric acid added to them to be safely preserved, the flavor of the sauce will also be a lot more acidic and not as sweet.
The plus side is that you can make this sauce even when tomatoes aren’t in season and you don’t have to cook it as long if you use canned tomatoes.

No garlic in tomato sauce? That can’t be right!

I know, I know. This is very unconventional and, to be honest, I don’t think I’ve ever made tomato sauce without garlic until this time. My mom shared this with me and I decided to trust her. It was a game changer. I love garlic with tomatoes, but I loved the flavor with just the sweet, sauteed onions.
Just give it a try – you can always add some garlic in later, if you like. Saute the garlic in some oil for 30 seconds – 1 minute until fragrant, then pour in the sauce.

Can this tomato sauce be preserved/canned?

Per the canning standards, tomato products need an acid to be canned safely. (That’s why canned tomatoes have citric acid added to them.) I personally prefer the flavor of this sauce without lemon juice, citric acid or vinegar, so I choose not to can it. So that’s why I simply store some of the sauce in my refrigerator and the rest I put in my freezer.

I store the tomato sauce that I keep in my refrigerator in glass mason jars. For freezing, I like using these twist top containers*. They are great for broth and sauces, don’t spill over, even if they fall over. They are also air tight and will keep your sauce fresh. (I like the 4 cups containers for this sauce.)

*affiliate links


Easy Tomato Onion Sauce

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This easy tomato onion sauce is made with just 3 ingredients – onions, tomatoes and olive oil. The onions are cooked until they are tender and sweet, then simmered in the tomatoes. It’s delicious as a pasta sauce, but I also love adding it to many other recipes.

  • Author: Olga’s Flavor Factory
  • Prep Time: 30 min
  • Cook Time: 2 hours 30 min
  • Total Time: 3 hours
  • Yield: 10 cups 1x



6 lbs tomatoes, peeled, seeded and cored (cut into 46 pieces)

3 lbs onions, sliced into half circles

1/4 cup olive oil

salt, ground black pepper, to taste

fresh herbs, for serving (basil, parsley, etc.)


  1. Prep the tomatoes by washing, coring and slicing them into quarters. (I like to peel the tomatoes and remove the seeds first, but you can skip this step if you don’t mind the seeds and skin. This is a personal preference.)
  2. Slice the onions into half circles. 
  3. Heat the oil until shimmering, then add the onions. Season to taste with salt and ground black pepper. Cook on medium low heat until soft and turning slightly golden. (This will take about 15 – 30 minutes, depending on the size of your pot – if it’s wider, it will be faster, since there is more surface area for the onions to cook and for the excess liquid to get concentrated and evaporate.) (Keep the pot covered at first so that the onions cook through faster, then uncover, half way through, so the onion liquid will cook off faster. 
  4. Add the tomatoes with the tomato juice. Season with salt and ground black pepper as well. Bring everything to a boil, reduce the heat to a simmer and cook, covered, for about 2 hours. 
  5. Puree the sauce with an immersion blender or a regular blender, in batches, until it is the consistency that you like. 
  6. Add fresh herbs before serving. 
  7. To store, keep it in the refrigerator for about a week or freeze for up to 6 months. 

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