Cut half an onion into slices and fry for 3 minutes, then place on a piece of kitchen paper to drain off the fat. Now add the Leberkäse and the egg to the pan and fry and toast the toast on a medium setting.
When the toast is ready, cover it with the slice of Gouda cheese and the onion slices and then place the meat loaf on top.
Fry the egg depending on the desired firmness. I recommend searing it so far that the egg yolk is still slightly runny. Now salt and pepper the egg and place on the meat loaf. Finally, the second slice of toast on top, cut once diagonally and serve.