Steak Sandwich With Grilled Onions

Ingredients

• 1/4 cup soy sauce
• 1/4 cup balsamic vinegar
• 1 tablespoon brown sugar
• 1 teaspoon fresh thyme leave
• 1/4 teaspoon ground pepper
• 1 (1 1/4 lb)  beef flank steak
• 1 medium red onion, cut into 4 thick slices
• 8 slices sourdough bread, toasted on grill if desired
• 2 medium tomatoes, sliced
• 1 bunch arugula, tough stems discarded

Directions

1. 1

   In large self-sealing plastic bag, mix soy sauce, vinegar, sugar, thyme, and pepper.

2. 2

   Add steak to marinade, turning to coat.

3. 3

   Seal bag, pressing out excess air.

4. 4

   Place bag on plate; let stand 15 minutes at room temperature or 1 hour in the refrigerator, turning over several times.

5. 5

   Meanwhile, for easier handling, insert 1 long metal skewer horizontally through onion slices; set aside.

6. 6

   Prepare charcoal fire or preheat gas grill for covered direct grilling over medium heat.

7. 7

   Remove steak from marinade; pour marinade into 1-quart saucepan.

8. 8

   Heat marinade over high heat to boiling; boil 2 minutes.

9. 9

   Place steak and onion slices on hot grill rack.

10. 10

    Cover grill and cook steak and onion 12 to 15 minutes or until onions are browned and tender and meat is medium-rare, brushing both with marinade occasionally and turning both over once.

11. 11

    Transfer steak to cutting board; separate onion into rings.

12. 12

    Thinly slice steak diagonally across the grain.

13. 13

    Arrange onion rings and steak on 4 slices of bread; spoon any meat juices from board over onion and steak.

14. 14

    Top with tomatoes, arugula, and remaining 4 slices of bread.