Method:
Preheat oven to 400°F. Line a baking sheet with parchment paper.
In a small bowl, whisk together mayonnaise, lime juice and cayenne. Stir in cabbage and set aside.
Halibut fillets can vary greatly in size, make sure to cut so they will fit nicely in sandwich rolls. If more than 3/4-inch thick, carefully slice crosswise in half to create 2 thinner pieces of fillet.
In a small bowl, whisk egg whites until foamy. Place cornmeal, paprika and salt in a shallow bowl or baking dish. Dredge fish in egg whites, allowing any excess to drip off. Place in cornmeal mixture, turning to coat both sides. Set on a plate until all fillets are coated.
Heat oil in a large skillet over medium-high heat. Add coated fillets and cook until just browned, 2 minutes per side. Transfer to prepared baking sheet and bake about 8 minutes longer or until fish is opaque throughout. Serve on rolls topped with slaw.