Slow Cooker Fresh Tomato Sauce

1. Preheat broiler. On a large rimmed baking sheet, toss onion, carrots and olive oil. Spread the veggies in a single layer. Broil until onion begins to caramelize, about 15 minutes.
2. In a slow cooker, add onion and carrot mixture. Mix with the rest of the ingredients. Put lid on slow cooker and turn to low. Cook for 4 hours. Mix and turn on high. Cook for another 4 hours. Turn off slow cooker. Using a hand blender, puree the tomato sauce until no large chunks remain.
3. If freezing, let it cool completely and freeze in heavy duty plastic bags.