Preheat oven to 350°. Place all dry ingredients in a mixing bowl. Add the sweet corn and onions. Mix thoroughly. Combine soymilk and vinegar, and let sit 2 to 3 minutes. Combine dry and wet ingredients, and mix again. Lightly oil a cast iron skillet or 8" x 8" baking dish. Pour the cornbread batter into the skillet or dish. Bake for 35 minutes. Remove, slice and place on a serving platter.
Per serving - 228 calories, 7 g fat (28% calories from fat), 6 g protein, 37 g carbohydrate, 2 g fiber, 0 mg cholesterol, 334 mg sodium