Quarter the feta cheese. Cut the tomato and onion into slices. Now place the feta cheese on a piece of aluminum foil, put a slice of tomato and, if you like, onion rings on top. Season with a little salt and pepper and completely wrap in the aluminum foil. Then place on the preheated grill and grill until the cheese is soft. This takes about 10 minutes.
Note from the chef`s recipe editing: If you don`t want to use aluminum foil, you can use parchment paper or baking paper for the packets. If you use lemon juice and salt, this is recommended for health reasons.