1.Stir Together The Mayonnaise, Onion, Tomato, Relish, And Piri Piri In A Small Bowl. Season To Taste With Salt And Pepper, And Set Aside. 2.Season The Tilapia Fillets On Both Sides With The Seafood Seasoning And Garlic Powder. Melt The Butter In A Skillet Over Medium Heat. Cook The Tilapia Fillets Until They Are Golden Brown On Both Sides And No Longer Translucent In The Center, 2 To 3 Minutes Per Side. Place Two Slices Of Pepperjack Cheese On Top Of Each Fillet, Cover The Skillet, And Cook Until The Cheese Has Melted. 3.Place Each Tilapia Fillet Onto A Slice Of Toasted Bread, Spread With The Reserved Sauce, Then Top With The Remaining Slices Of Bread.