Preheat oven to 425 degrees. Line a baking sheet with parchment paper.
In a shallow dish, combine melted butter and mustard.
In a separate shallow dish, combine crushed crackers, cheese, and salt.
Coat tilapia in butter mixture; dredge in cracker mixture. Place on prepared baking sheet, and bake for 6 minutes. Turn fish stick, and bake for 6 minutes longer, or until golden brown. Serve immediately.