Slice 50 g of red onion and place in into the large bowl. Then, thinly slice 1 lemon and add to your onion. Then, season with salt and pepper. Mix that a good mix. Place the mixture on a large piece of tin foil. Make sure that you leave a little bit of mixture to decorate your cooked fish.
Take 500 g of salmon fillet. Put the fillet on the lemony mixture. Pour 30 ml of unsalted butter on your salmon. Sprinkle 15 g of dry Italian herbs. Season with salt and pepper.
Wrap the fish into the tin foil.
Put your salmon on the grill and cook for 15 minutes at medium-high heat. Let the fish rest for 5 minutes. Spoon your lemony mixture over grilled fillet.