Preheat the oven to 400 degrees. In a bowl, combine the salt, pepper, garlic powder, paprika and chili powder.
Lightly spray the halibut with olive oil. Coat the fish on all sides with the spice mixture then place on a parchment lined baking sheet, or a lightly greased baking dish. Bake for 15-20 minutes, until fish flakes easily with a fork.
While the fish bakes, make the avocado salsa. Add the diced avocados, red onion, jalapeño, lime juice, salt and cilantro to a bowl and toss well. When fish is done baking, serve with avocado salsa on top and enjoy!