Preheat the oven to 400ºF. Place a cooling rack on a baking sheet and spray lightly with cooking spray. Set aside.
In a small bowl, combine the ¼ cup mayonnaise, pickle relish, mustard and onion powder. Stir to combine. Season to taste with pepper. Refrigerate until ready to use.
Place the egg in a shallow bowl and add a splash of water. Lightly beat with a fork. In a second bowl, combine the Panko breadcrumbs and the Creole seasoning. Dip each of the shrimp in the egg, then into the breadcrumb mixture, using your hands to press the crumbs into the shrimp to coat. Place in a single layer on the cooling rack. Bake in the preheated oven until the shrimp are cooked through, about 6 minutes.
Meanwhile, combine the broccoli slaw mix, crushed pineapple and green onions. Add the mayonnaise and 3 tablespoons of the reserved pineapple juice. Stir to mix.
To serve, spread some of the homemade tartar sauce on the bottom of each bun. Top with tomatoes, shrimp, and then some of the pineapple slaw.
