Prepare the grill and allow the steaks to reach room temperature. In the meantime, dice the watermelon pulp. Put it in a bowl with all the other salad ingredients and scoop gently.
For the garlic bread, mix the garlic, parsley and butter and season to taste with salt and pepper. Cut the baguette diagonally into slices about 2 cm thick and spread the garlic butter on one side of each slice.
Roast the steaks on direct heat for about 5 minutes on each side and turn them halfway through a quarter turn to create a nice grill pattern. At the end of the grilling, let the steaks simmer on the edge of the grill at 65°C (149°F) core temperature.
As soon as the steaks are on the grill, spread the slices of bread on the edge of the grill with the buttery side up and roast them until they are crispy. Serve everything together with the watermelon salad.