Cook bacon. Remove from the skillet and drain then crumble it. Reserve the drippings.
Saute onion and jalapeno in bacon drippings for 3 to 4 minutes or until they begin to soften. Remove the onion and jalapeno to a platter. Place the skillet in your oven to heat (add oil if there isn't enough bacon grease in it.)
In a bowl combine cornmeal, flour, baking powder, salt, and sugar.
Combine milk, eggs, and butter in another bowl.
Pour the milk mixture along with the bacon, onions, jalapenos, and cheese into dry ingredients (cornmeal, flour, baking powder, salt, and sugar) and stir until just combined. Do not over-mix.
Pour batter into hot skillet.
Bake 23 to 25 minutes. Top will not get very brown. Cornbread is done when a wooden pick inserted into the center of the cake comes out clean or with dry crumbs.