Place chilies on baking sheet. Broil 3 inch from heat 15 minutes or until blackened and charred turning once.
Place chilies in ice water and chill 5 minutes. Drain well; peel and discard skins. Cut a 4 in slit in the side of each chilie; discard seeds and set aside.
Combine ricotta cheese, corn, green onions, pepper and half of garlic, stir well. Put 1/3 cup of mixture into each chilie. Arrange chilies in a small baking dish. Bake at 350 degrees for 20 minutes or until thoroughly heated.
Coat a small saucepan with cooking spray; place over medium heat until hot. Add remaining garlic and chopped onion sauté 3 minutes. Add cumin and oregano sauté 1 minute. Stir in salt and tomatoes.
Reduce heat and simmer, uncovered for 10 minutes more, stirring frequently. Pour sauce over chilies and serve.
