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.



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. 

Keywords: easy tomato sauce, homemade tomato sauce, homemade tomato sauce with fresh tomatoes, tomato onion sauce