Finely chop the onions. Roast the bacon cubes brown without adding any fat. Add the butter and onions and sauté briefly. Let it cool down, but the butter should still be liquid. Add eggs and buttermilk, stir well. Mix the flour, baking powder, sugar and salt in a bowl. Mix well with the other ingredients.
Grease a muffin sheet or place 2 paper baking tins for each muffin and place on a baking sheet. Fill the dough up to two thirds into the molds. Sprinkle with cheese if necessary.
Baking: approx. 25 minutes in the middle of the oven preheated to 180 ° C. Serve hot or chilled.