Alternate cooking methods: Layer the tomatoes and all the vegetables and seasonings in a deep baking dish or Dutch oven. Cover and bake at 275 degrees F (135 degrees C) for about 3 hours. Towards the end, stir in tomato paste and adjust seasoning, then uncover and return to the oven until liquid reduces as much as desired.
Do the same thing, but in a slow cooker, either on high for 3 to 4 hours or on low for 6 to 8 (or all day). Again, add the tomato paste and uncover to reduce the liquid.
Try using a Reynolds® slow cooker liner in your slow cooker for easier cleanup.