Preheat oven to 400°.
Place a small nonstick skillet coated with cooking spray over medium heat until hot. Add onion; sauté 5 minutes or until lightly browned. Combine onion, whole-kernel corn, cream-style corn, hominy, chiles, and cilantro in a large bowl; stir in 1/2 cup cheese and egg substitute. Spoon mixture into a 9-inch pie plate coated with cooking spray. Combine 1/4 cup cheese and cornflakes; toss well. Sprinkle over corn mixture.
Bake at 400° for 50 minutes or until top is browned and mixture is set. Serve with 1 tablespoon sour cream.