Place chiles on a baking sheet. Broil 3 inches from heat 15 minutes or until blackened and charred, turning once.

Place chiles in ice water, and chill 5 minutes. Drain well; peel and discard skins. Cut a 4-inch slit in the side of each chile; discard seeds, and set aside.

Combine ricotta cheese, corn, green onions, pepper, and half of garlic; stir well. Spoon 1/3 cup of the cheese mixture into each chile. Arrange chiles in a small baking dish. Bake at 350 degrees F for 20 minutes or until thoroughly heated.

Coat a small saucepan with cooking spray; place over medium-high heat until hot. Add remaining garlic and chopped onion; saute 3 minutes. Add cumin and oregano; saute 1 minute. Stir in salt and tomatoes.

Reduce heat and simmer, uncovered, for 10 minutes more, stirring frequently. Pour sauce over chiles and serve.