1 medium ripe avocado, peeled and cut into 1/2″ dice
1 medium ripe mango, peeled and cut into 1/2″ dice
1 cup cherry tomatoes, quartered
4 large fresh basil leaves, thinly sliced
3 tablespoons extra-virgin olive oil, divided, plus more for brushing
3 tablespoons fresh lime juice, divided
Kosher salt and freshly ground black pepper
4 6-ounce halibut or mahi-mahi fillets
4 lime wedges
Prepare a grill to medium-high heat. Gently combine the avocado, mango, tomatoes, basil, 1 tablespoon oil, and 1 tablespoon lime juice in a large mixing bowl. Season salsa to taste with salt and pepper and set aside at room temperature, gently tossing occasionally.
Place fish fillets in a 13x9x2″ glass baking dish. Drizzle remaining 2 tablespoon oil and 2 tablespoon lime juice over. Season fish with salt and pepper. Let marinate at room temperature for 10 minutes, turning fish occasionally.
Brush grill rack with oil. Grill fish until just opaque in center, about 5 minutes per side. Transfer to plates. Spoon mango-avocado salsa over fish. Squeeze a lime wedge over each and serve.