Preheat the oven to 375 degrees Fahrenheit. In a small pan heat up 2 tablespoons of the butter and add the diced onions and stir so that the onions are coated in the butter. Reduce the heat to the lowest setting. Allow the onions to cook for about 35-45 minutes, stirring every ten minutes or so, until they are a dark golden color. Remove them from the heat and set them aside.

In a medium sized bowl, mix together the corn meal, flour, sugar, salt, and baking soda until well blended. Set aside.

In a large bowl, mix together the sour cream, milk, creamed corn, and remaining 4 tablespoons of butter until completely combined. Stir in the dry ingredients, onion-butter mixture, jalapeno, and 1/2 cup of the cheddar cheese. Pour the mixture into a greased cast iron skillet (mine is about 7 inches in diameter and 3 inches deep) and sprinkle the remaining cheese over the top of the cornbread.

Place the pan in the oven and bake for 35-40 minutes or until a toothpick inserted into the cornbread comes out clean. Remove from the oven, allow to cool for 10 minutes, cut into slices, and serve.