Mix Mayo and Sour Cream. Cut up fresh dill and mix in. Season with lemon pepper, Set sauce aside.
Lay Steelhead filets in baking dish. Place sliced onion, sliced Habano pepper, and minced garlic on top of filets. Squeeze juice of lemon over filets. Cover with sour cream sauce. Arrange sliced tomatos on top and cover with foil. Bake at 400 degrees for 45 minutes or until fish easily flakes.