Preheat a grill or a grill pan to medium-high. Cut the skin off the fish steaks and cut away any deeply colored or veined connective tissue. Cut the fish into 1-inch cubes and place in a shallow dish. On a cutting board, pile the garlic, lemon zest and parsley and finely chop the ingredients together, combining their flavors. Liberally douse the fish with EVOO and slather with the garlic-parsley mixture. Let the fish hang out for about 10 minutes. skewer the fish cubes, season with salt and pepper and grill until firm and opaque, about 3 minutes on each side.
While the fish is working, combine the tomatoes and arugula and dress with the lemon juice, EVOO and salt and pepper to taste.
When the fish is cooked, remove from the heat and let rest for 2 to 3 minutes; remove from the skewers. Place the fish across the top of the salad and serve with the lemon wedges.