
Rub the fish with lemon juice, garlic, salt, and pepper. Rest 15 minutes.
Grill or pan-sear over medium-high heat, about 5 minutes per side, until the flesh flakes.
Heat the oil, soften the onion, add the tomato, then the greens. Cook 4 to 5 minutes until just wilted.
Serve the fish over the greens with the pan juices.