This method is super easy, relies on the slow cooker so you can avoid heating up your range, and delivers on the classic Italian flavor.
– Fresh tomatoes: Paste tomatoes or heirloom tomatoes both work. – Garlic – Basil – Salt
Fill the slow cooker with the chopped fresh tomatoes, stems discarded, and the garlic. Cover and cook on low overnight, or about 8-10 hours.
Remove the lid and let cool for 30-60 minutes. (This makes it possible to blend them without the risk of the steam making your blender explode, which is key.)
Use a large slotted spoon or small mesh spoon to scoop out the tomato solids and garlic into a blender, leaving the liquid in the slow cooker.
Add oregano, salt, olive oil, and basil and blend into a smooth sauce. (You may need to do two batches.) Blend very, very well to ensure that the skin is blended up.
Pour into freezer containers or storage bags and freeze for up to 1 year. Thaw overnight in the fridge.
Don’t worry if it looks a little separated—it will come back together when it’s warmed. Heat a pot over medium heat, add sauce, and simmer for 10-15 minutes.