Heat a pot over medium heat. Once heated, add in the olive oil and onions. Cook until the onions just start to become translucent. For best flavor, it is best if a couple onion pieces just start to brown but do not burn the onions.
2 Tablespoons olive oil, 1 yellow onion
Add in the garlic and sauté for one minute stirring often.
4 cloves garlic
Carefully pour in the broth - it will sizzle when you first start pouring it and the steam will be hot, do not keep your hand directly over the pot.
1 cup chicken broth
Add in the Italian seasoning, salt, pepper, sugar and red pepper flakes. Stir well to mix
1 Tablespoon Italian seasoning, ½ teaspoon salt, ½ teaspoon black pepper, ½ teaspoon sugar, ¼ teaspoon red pepper flakes
Add in the tomato puree and diced tomatoes. Stir well until completely mixed and add in the bay leaf.
Bring to a simmer on medium and drop the heat to low - medium low. Temperature depends on your stove. You want it to simmer gently. Simmer for at least 25 minutes (longer is ok but not required.)Remove bay leaf and your sauce will be ready for your lasagna.
Notes
Nutritional values are estimated and based on approximately 6 cups of sauce. It will be between 5 and a half to 6 cups prepared. If you add a meat it will make between 7 and 8 cups depending on the meat and how much you add. Salt - You may need to adjust the salt for you preferred taste and also based on the amount of sodium in the other ingredients you use. You can start with a little and taste the sauce often to see if you need more.A note about the sauce - This was originally written for crockpot lasagna where you don't boil the noodles (the noodles will cook in the sauce), but you can use it in a regular lasagna. You will find that it may make a little bit too much for you if you are making baked lasagna. You can freeze any remaining sauce or even serve it at the table if anybody likes extra sauce. If you like a lot of sauce, this will be the perfect amount!If you add meat - We add sausage to our lasagna sauce, but that is optional and not listed in the ingredients. You can add ground sausage, links or even ground beef. Cook the meat separately to remove most of the grease and add it with the tomatoes. Cook the sauce as directed above.Important - Always remove the bay leaf and never attempt to eat it. Bay leaf is great to cook with but dangerous if you swallow it whole. It can be left out of this lasagna sauce recipe if you prefer, but we think it adds a great flavor. It is safe to cook with but does not break down in the body (or in liquid when cooking with it) and can cause tearing internally.