Fill an 8-quart / 7.5 L stockpot with about 4 liters of water and stir in the 60 g coarse salt so the water tastes like the sea. Bring to a rolling boil.

While the water heats, slice the red onion thin and place it in a bowl of cold water with the red wine vinegar. Let it sit at least 10 minutes, then drain well.

Plunge the lobsters headfirst into the boiling water one at a time. Cook for 12 to 15 minutes, until the shells turn bright red and an instant-read thermometer in the thickest part of the tail reads 140 F / 60 C.

Lift the lobsters out with tongs and drop them straight into a large bowl of ice water. Let them cool completely, about 10 minutes, to stop the cooking and firm up the meat.

Once cool, twist off the tails and claws. Use kitchen shears to cut along the underside of the tail shell and lift the meat out in one piece, then crack the claws and remove that meat too.

Slice the tail meat crosswise into thick medallions. Halve the empty lobster shells lengthwise if you want to serve the salad on the shell.

Arrange the lobster meat over the shells or on a platter. Scatter the drained onion and diced tomato over the top.

Whisk the olive oil, lemon juice, a pinch of fine salt, and black pepper in a small bowl. Drizzle it over the lobster and vegetables.

Sprinkle with chopped parsley and chill for 15 to 20 minutes before serving. Eat within a few hours for the best texture.