In a cast iron pan, fry the onions till they are a little brown, soft and aromatic.
In a mixing bowl, combine corn, butter and eggs.
Add the dry powder, mix thoroughly.
Add the onions and peppers.
Pour it all in the cast iron pan, and bake at 350 for 50-60 minutes, or till toothpick inserted in the middle comes out clean and dry.
Notes
I use bacon fat, of course, to fry the onions. The remaining caramelized onion bits and bacon grease makes for a real nice crust on the underside of the cornbread.