Peel and finely dice the onions. Heat 1 tbsp. oil and let half of the onions caramelize slightly. Add tomatoes, bring to the boil and simmer for about 10 minutes, stirring continuously. Season to taste with barbecue sauce, vinegar, salt, sugar and cayenne pepper.
Peel, wash and slice the potatoes. Grate parmesan. Mix potatoes and cheese and season with salt. Spread flat on a baking tray lined with baking paper. In a preheated oven (electric cooker: 200 °C/ circulating air: 175 °C/ gas: see
manufacturer) bake for about 40 minutes until crispy. Turn with a spatula in between.
Wash, clean and finely dice all but one of the peppers. Finely dice the cheddar. Mix cheese, pepperoni and crème fraîche. Knead minced meat, remaining onion cubes, breadcrumbs, 4 tablespoons of water, egg and mustard to a smooth dough, season with salt and pepper.
Form into 4 meatballs and fill each with 1/4 of the cheese mixture. Heat 6 tablespoons of oil in a frying pan and fry the meatballs for about 10 minutes while turning. Remove from the pan, push the potatoes together on the baking tray, spread the meatballs on top and cook for the last 10 minutes.
Cut the remaining peppers into thin rings. Arrange potatoes, meatballs and tomato sauce. Sprinkle with pepperoni rings.