Don't let the mayo atop this whitefish scare you off. It cooks up brilliantly and creates a golden, flavorful topping. Use this method on just about any flakey white fish. Serve with corn on the cob, new potatoes with dill, green beans, and good bread. A dessert of blueberry cobbler would be just fine too.
Heat the oven to 400°F. Arrange the racks with one in the middle of the oven, and one near the broiler.
Clean the fish by very swiftly rinsing it under cold water, then patting it dry gently and thoroughly with a paper towel.
Line a heavy sheet pan with foil and place the filets on the foil lengthwise.Squeeze the lemon over the filets evenly. Season with salt and pepper. Stir the mayonnaise in a small bowl until smooth. Using the back of a spoon, spread the mayo over the fish (it will be slippery against the wet surface of the fish; keep spreading. It won’t be perfectly even). Dust the fish with paprika.
Bake the fish for 10 minutes. Turn the broiler on and move the pan to the top rack. Broil until golden and bubbly, 1-2 minutes longer. Cut each filet into thirds and serve immediately.