Bake the Tomatoes: Preheat your oven to 400°F (200°C). Start by washing your fresh tomatoes and cutting them in half. Place the halved tomatoes on a baking sheet, cut side up. Bake them in the preheated oven for about 30 minutes. This roasting step enhances the flavor and sweetness of the tomatoes, and removes excess juice making your sauce rich and delicious.
Blend the Ingredients: Once the tomatoes are roasted, remove them from the oven and let them cool slightly. In a blender or food processor, combine the roasted tomatoes, diced onion, fresh basil leaves, pepper salt, and garlic powder. Blend until smooth, adjusting the seasoning to your taste. If you prefer a chunkier sauce, you can pulse the mixture a few times instead of blending it completely.
Slow Cook for flavor and Texture: Transfer the blended mixture to a crock pot. Set it to low and let it slow cook for about 10 hours. This slow cooking process allows the flavors to meld beautifully, creating a rich and savory sauce. Be sure to stir the sauce occasionally to prevent it from sticking to the sides.
Serve and Enjoy: After 10 hours, your marinara sauce will be thick, flavorful, and ready to serve! Use it immediately with your favorite pasta, as a pizza sauce, or as a base for other dishes. You can also store any leftovers in airtight containers in the refrigerator for up to a week or freeze them for later use.
If you decide to water bath can, place them in the canner for 25 minutes, depending o location. Then place on a thick towel on the counter and let sit for 24 hours. Check the seals before storing.