Place steak into freezer for an hour or until firm but not frozen solid. Remove steak from freezer and slice into thin strips. Combine garlic, onion, pepper, mustard, soy sauce, worcestershire, pineapple juice and rum in a sealable container. Add steak and marinate in refrigerator overnight, rotating at least once.
Remove from refrigerator and let it come to room temperature. Discard marinade and place strips in a single layer onto a large, oiled, oven-safe cooling rack. Place rack onto a foil-lined baking sheet and bake at 175°F for up to 6 hours or until jerky is completely dry.
Serve immediately or store once cooled.