In the bottom of a mixing bowl, whisk together the milk and cornmeal and set aside. Let the mixture rest for 15 minutes. While this is resting, mix together the flour, baking powder, and salt and set aside.
Preheat the oven to 400 degrees. Add the dry ingredients to the milk and cornmeal mixture and stir to combine. Add the egg and the oil and beat with an electric mixer on medium speed for 10 minutes. (This amount of time is required. The cornbread won't be nearly as fluffy and moist without the full beating time.)
Grease an 8x8 or 7x10 pan with butter and pour the batter into it. I have used a small 8" cast iron skillet as well and it works great. Doubling the recipe will perfectly fill a standard cast iron skillet or a 9x13 pan. (If doubling the recipe use a TOTAL of 3 teaspoons of baking powder.)
The secret to this cornbread is in the method. The soaking of the cornmeal combined with the beating process makes this the amazing cornbread that it is. Don't let the slightly longer process deter you from trying this. This is a simple and straightforward recipe: soak, stir, beat, and bake. The extra step is worth it! Whether you are baking a gluten free version or not, be careful to follow all of the steps in the directions.