Defrost the Turkey meatballs and cut 2 notches on each of them with a knife. Do not cut through completely.
Fry the balls at 160°C until golden brown.

Cut the onion in brunoise cuts.

Pipe a little mayonnaise and ketchup into the notches.

Stick in a fork and scatter red onion over it.

You can add a personal touch by sprinkling more herbs on; for example satay herbs, ras el hanout, ...