Homemade roasted tomato sauce is incredibly easy and flavorful - let your oven and blender do the heavy lifting!
Preheat your oven to 400 degrees and begin prepping the tomatoes, garlic, and onions. Slice the tomatoes in half and cut the top quarter off of the head of garlic
Place the vegetables and thyme on a large baking sheet and add olive oil, salt, and pepper. Stir everything together to coat. Divide the mixture evenly between two baking sheets to roast.
Turn all the tomatoes flesh side up and roast at 400 degrees for 20 minutes.
After 20 minutes, rotate the pans to help the vegetables cook more evenly and roast an additional 20 minutes.
Remove from the oven and allow the pans to cool. When the garlic is cool enough to handle, pop the individual cloves out of their paper. Remove the roots from the roasted onion quarters.
Add the roasted vegetables and stock to a large blender or food processor. Blend thoroughly for 60-90 seconds.
At this point, you can either use the sauce as is or you can strain it to remove the puréed seeds and skin. If you are going to strain it, I recommend adding an additional 1/2 cup of broth or stock to help beef up the sauce.