Preheat your cast iron skillet on medium-high heat and preheat the oven to 400F.
Over butter or oil, sauté onions until soft and edges get brown (5-10 min).
Add in ground beef and salt and cook all the way through until all is browned.
While the meat is cooking, prepare the topping mixture in a bowl. Mix together sourdough starter, eggs, salt, garlic powder, butter, and baking powder (no cheese yet). It kind of looks like pancake batter.
Once the meat is fully cooked, add in bell peppers and cook for 1-2 minutes.
Pour sourdough mixture on top, then sprinkle cheddar cheese over top.
Put entire skillet in oven for 25 minutes (cheese will be a tad crispy).
Enjoy!