Heat the oil in a large skillet over medium heat. Add the onion and garlic; cook and stir until the onion is tender. Stir in the cumin, chili powder, cinnamon, cocoa powder, and flour; cook for 1 minute.
Stir in the tomatoes with juice and chicken broth. Bring to a boil; reduce heat to low and simmer for 20 minutes.
Stir in the raisins if desired. Simmer for an additional 5 minutes.
Spoon the mixture into lightly greased baking dishes. Cover with foil and bake at 350 degrees F (175 degrees C) for 25 minutes.