Preheat oven to 400°.
Coat a 9-inch cast iron skillet with 1 teaspoon oil; place in oven 10 minutes.
Combine cornmeal mix and onion in a medium bowl. Combine buttermilk, 2 tablespoons oil, egg substitute, and corn. Add to cornmeal mixture, stirring just until moist. Spoon batter into preheated pan. Bake at 400° for 20 minutes or until golden. Cut into 8 wedges.