Slow Cooker Fresh Tomato Sauce

  • Author: Kelley


An easy way to make tomato sauce using fresh tomatoes and the slow cooker!


  • 1/2 cup olive oil
  • 6  cloves garlic, minced
  • 2 medium onions, diced (about 2 heaping cups)
  • 8 lb tomatoes, washed, cored, and quartered (about  16 cups)
  • 6 oz tomato paste
  • 1/4 cup, packed fresh basil leaves
  • 2 tablespoons sugar
  • 1 tablespoon Italian seasoning
  • kosher salt to taste


  1. In a large saute pan, heat olive oil over medium-low heat. Add onion and sauté about 10 minutes, stirring often, until onion is soft and translucent. Add minced garlic and cook for 1 minute more. Remove from heat.
  2. Meanwhile, clean, core, and quarter the tomatoes. I  live the skins on- the natural pectin in the skin will help thicken the sauce. I don’t worry about removing seeds as they don’t bother me after I puree the sauce but feel free to remove if you’d like!
  3. Add the quartered tomatoes to the base of the slow cooker. Add the sautéed onions and garlic, tomato paste, fresh basil, sugar, and Italian seasoning.
  4. Cover and cook on low for 4 hours. After 4 hours, the tomatoes will be falling part and lots of juice will have accumulated. In batches, transfer tomato mixture to a blender or food processor and blend until smooth. Return pureed tomatoes (now sauce!) back to the slow cooker and cover. Cook again on low for 3-4 hours until sauce has reduced a bit and the flavors are concentrated. Season to taste with salt and pepper.
  5. Store tomato sauce in glass jars or freeze in ziplock or other freezer friendly container. The sauce will keep in the fridge for a few weeks. This is amazing on it’s own or it’s a great starter for a soup. I used the sauce over pasta, as a topping on stuffed zucchini and I finished off the last bit in some turkey chili. It’s super versatile!