Preheat the grill. In a bowl, combine 4 cups water with the lemon juice and 1 tablespoon salt. Trim and peel the salsify. Cut into small sticks, and place in the bowl with the lemon water. Set aside to soak for about 10 minutes.

Meanwhile, rub the sea bream with the olive oil, and season with salt and pepper. Place on the grill, and cook for 10 minutes on each side.

Meanwhile, in a skillet over medium heat, warm 2 tablespoons butter. Drain the salsify, and dry it well. Add to the skillet, and sauté until golden, about 6 minutes. Add 2 tablespoons water, cover, and continue to cook for another 3 minutes. Deglaze with the vinegar, add the remaining 2 tablespoons butter, and cook until the sauce starts to thicken. Remove from the heat, and set aside. Peel the orange and grapefruit, and cut into sections. (Make sure that all the outer white pith is removed). Cut into smaller pieces, and set aside.

Transfer the grilled sea bream to a serving platter. To serve, distribute the salsify and citrus pieces around the fish, and garnish with the dill.