Wash and prep all the vegetables.- Cut the tomatoes in half. Doing this allows the moisture to escape so you don’t end up with a watery sauce.- Cut yellow onion into large chunks (about 1 inch).- Peel garlic cloves (no need mince).- Peel carrot and cut into large chunks (about 1 inch).
Place all vegetables in a large stainless steel or glass roasting pan or two small ones. You'll want to makes sure that there is plenty of room and high sides (2-3 inches) as a lot of liquid cooks out.
Drizzle the olive oil over the vegetables and sprinkle on the Italian seasoning, salt, and red pepper flakes. Mix together.
Put the pan(s) in the oven and roast for 40-45 minutes until the ends of some vegetables start to char.
Remove the pan(s) and let rest for 5-10 minutes.
Scoop the vegetables in a blender with a slotted spoon, leaving any water behind to ensure the sauce is think. Blend until desired consistency and add some of the pan liquid if it’s too thick for your liking. Make sure to do this in batches so it doesn’t explode everywhere. Add to your favorite pasta and enjoy!
Notes
Note—do not use aluminum pans as the tomato acid can wreck the pans. Use something that stands up to acid, like stainless steel or glass.In addition to using this as a traditional pasta sauce, use it on pizzas, as a soup base for tomato-based soups, or as a dipping sauce.