Rum-Pepper Steak Sandwiches

• Marinade:
• 1/2 cup dark rum
• 2 tablespoons brown sugar
• 1 tablespoon coarsely ground black pepper
• 1/4 teaspoon salt
• 5 garlic cloves, crushed, or 2 1/2 teaspoons bottled minced garlic
• 1 (1 1/2-pound) flank steak
• Flavored mayonnaise:
• 1/2 cup fat-free or light mayonnaise
• 2 teaspoons prepared horseradish
• Remaining ingredients:
• 8 (1/2-inch-thick) slices red onion (about 2 onions)
• 16 (1-ounce) slices sourdough bread
• 2 cups thinly sliced romaine lettuce
• 16 (1/4-inch-thick) slices tomato (about 3 tomatoes)

1. To prepare marinade, combine first 5 ingredients in a large zip-top plastic bag. Trim fat from steak, and add steak to bag. Seal and marinate in refrigerator at least 2 hours, turning bag occasionally. Remove the steak from bag, reserving marinade. Pour the marinade into a microwave-safe dish. Microwave marinade at HIGH 1 minute or until mixture boils.
2. To prepare flavored mayonnaise, combine mayonnaise and horseradish, and set aside.
3. Prepare grill.
4. Place steak and red onion slices on a grill rack, and grill onions 4 minutes on each side, basting with the reserved marinade. Remove onions from grill. Turn the steak, and grill an additional 8 minutes or until steak is desired degree of doneness. Remove steak from grill. Place bread slices on grill rack, and grill 2 minutes on each side or until toasted.
5. Cut steak diagonally across grain into thin slices. Spread 1 tablespoon flavored mayonnaise on one side of each of 8 toasted bread slices. Divide steak, onion slices, lettuce, and tomato slices evenly among 8 bread slices. Top with remaining bread slices.
6. Note: Substitute pineapple juice for rum, if desired.

marinade, dark rum, brown sugar, ground black pepper, salt, garlic, flank steak, mayonnaise, light mayonnaise, horseradish, remaining ingredients, red onion, bread, romaine lettuce, tomato

Taken from www.myrecipes.com/recipe/rum-pepper-steak-sandwiches (may not work)