Preheat the oven to 475° F/250° C. Cut the tomatoes in half and remove the seeds and juices. Arrange them cut side down on the baking sheet and brush with olive oil. Bake until the skins are evenly black all over, about 20 minutes. Remove from the oven and allow to cool in the pan. Discard the skins and transfer the tomatoes and the juices to the blender. Blend with the chiles and garlic until smooth.

While the tomatoes roast, heat the canola oil in the saucepan over medium heat. Add the onion and cook while stirring until the onion is soft and translucent, and 4 minutes. Add the tomato puree, cover, and bring to a boil. Stir in the salt and cinnamon stick, reduce heat, and cook uncovered at a simmer. Cook until the sauce is thickened, about 30 minutes. If sauce thickens too much, like a paste, reduce the heat slightly and add water a tablespoon or two at a time.