Cut the onions in half, then into slices about 1/4-inch wide. Separate into pieces. Place 2 tablespoons of butter in a 9 to 10 inch oven proof skillet over medium heat. Sauté the onions, stirring occasionally, until softened and they begin to caramelize and turn very brown. This will take about 10 minutes.
While the onions are cooking, microwave the bacon until crisp. When cooled, crumble and set aside. Remove onions from skillet. Melt remaining butter in the skillet. Remove from heat. Sprinkle with brown sugar and return the onions to the pan, covering the bottom evenly. Sprinkle the crumbled bacon on top of the onions.
In a medium size bowl, combine the flour, baking powder, salt, sugar and shredded cheddar. In a seperate bowl, whisk together the egg, milk, and oil until thoroughly combined. Add to the dry ingredients and stir together quickly, but completely. The batter is very thick, almost like a biscuit batter.
Preheat oven to 350 degrees F. Spread the batter, by the spoon full, over the onions evenly. Spread out the batter with the tines of a fork. Bake for about 35 minutes or until a toothpick inserted into the middle comes out dry. The top of the bread should be browned slightly.
Let stand for five minutes. Then place a serving dish, slightly larger than the bread, over the top of the bread and turn over like an upside down cake.
Slice and serve warm as a side dish or an appetizer
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