In a large saucepan cook onion and garlic in hot oil until tender. Drain off fat. Stir in the undrained tomatoes, olives, raisins (if using), the 2 tablespoons chili powder, and 1/4 teaspoon salt. Heat to boiling; reduce heat. Simmer, uncovered, about 20 minutes or until slightly thickened. Stir in cooked beef; heat through. Evenly spread beef mixture into an ungreased 3-quart rectangular baking dish; set aside.
Meanwhile, combine cornmeal and 1 cup cold water. Set aside. In a medium saucepan bring 2 cups water to boiling; add the 1/2 teaspoon salt and chili powder. Slowly add cornmeal mixture to boiling water, stirring constantly. Return to boiling, stirring constantly. Reduce heat to low. Cook for 10 to 15 minutes or until mixture is very thick, stirring occasionally. Spread the cornmeal mixture evenly over beef mixture. Bake, uncovered, in a 325 degree F oven for 20 minutes. Sprinkle with cheese. Bake for 5 minutes more. Let stand 5 minutes before serving. Makes 6 to 8 servings.