For a simple and flavorful sauce, it doesn’t get any better than this Crockpot Marinara Sauce. We start by sautéing onions and garlic and then layer in the seasonings. Then we add canned crushed tomatoes, tomato paste, and balsamic vinegar and let it all simmer in the slow cooker. The result is a homemade tomato sauce that has a surprising complexity of flavor. Make a big batch ahead and freeze it to have on hand when you need it
Heat a skillet to medium high heat. Add avocado oil and allow to heat for a minute. Add onion and cook for 8 to 10 minutes. Add the sweetener, Italian seasoning, red pepper flakes, salt, and pepper.
Reduce heat to low and cook for 10 more minutes. Add garlic and cook for one more minute.
Transfer to a slow cooker and stir in fire roasted tomatoes, tomato paste and balsamic vinegar. Cook for 2 hours on high or 4 hours on low.