Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Peel and coarsely dice onions. Halve sausage lengthwise and cut into slices.
Heat the oil in a large ovenproof pan. Steam onions and sausage for about 5 minutes. Add the tomatoes and chop with a spatula. Simmer for another 5 minutes. Season the sauce with salt and cayenne pepper to taste.
Wash and chop the parsley and stir into the sauce. Beat the eggs and let them slide into the pan on top of the sauce with a little distance between them. Leave to set in a hot oven for about 10 minutes. Flatbread tastes good with it.