In a skillet over medium heat, cook the bacon. Once cooked, remove the bacon and place on a paper towel to drain. Leave the drippings in the pan. Increase the heat to medium-high. Add onions, and saute for 5 minutes.

Preheat oven to 400 degrees. Prepare a 12 cup muffin tin with non-stick spray.

In a bowl combine buttermilk, olive oil, and egg.

In a separate bowl mix together flour, cornmeal, baking powder, baking soda, salt and cayenne. Make a well in the center, and add the buttermilk mixture. Stir until just combined.

Fold in bacon, onions, and cheese. Fill the muffin tin with batter. Bake for 13 minutes, or until a toothpick comes out clean.

Remove muffins and let cool on a wire rack.