1. Start by preheating your oven to 400°F. This ensures that the salmon cooks evenly.
2. Pat the salmon fillets dry with paper towels. Rub each fillet with olive oil, and season generously with salt and black pepper.
3. Heat a large oven-safe skillet over medium-high heat. Once hot, add the salmon fillets, skin-side down. Cook for about 3-4 minutes, until the skin is crispy.
4. Transfer the skillet to the oven and bake for an additional 5-7 minutes, or until the salmon is cooked through and flakes easily with a fork.
5. While the salmon is baking, prepare the mango salsa. In a medium bowl, combine the diced mango, red onion, jalapeño, cilantro, lime juice, and cumin. Stir gently to mix.
6. If using, fold in the diced avocado just before serving to keep it fresh.
7. Remove the salmon from the oven and let it rest for a minute. Spoon the mango salsa generously over each fillet before serving.

Cooking the salmon in the oven helps lock in moisture, ensuring it stays succulent. From my experience, using a skillet with a good sear gives the salmon a delightful texture that pairs well with the vibrant salsa.