Marinated Flank Steak Sandwiches

Ingredients

1 small white onion, sliced into 1/4-inch rings
1/2 cup fresh orange juice (from 2 oranges)
1/4 cup fresh lime juice (from 2 to 4 limes)
1/4 teaspoon ground cumin
2 garlic cloves, crushed
1 1/2 pounds flank steak, trimmed of excess fat
Coarse salt and freshly ground pepper, to taste
2 tablespoons unsalted butter, room temperature
1 loaf ciabatta (16 inches), split horizontally, halved crosswise
6 ounces Gruyere cheese, thinly sliced
1 whole dill pickle, thinly sliced crosswise

Directions

Step 1
Combine onion, juices, cumin, and garlic in a shallow dish. Add steak, and let stand, turning once, for 20 minutes.

Step 2
Preheat a grill pan to medium-high and oven to 400 degrees. Pat steak dry, and season with salt and pepper. Grill to desired doneness, 5 to 6 minutes per side for medium-rare. Let rest.

Step 3
Grill onion for 2 to 3 minutes. Discard marinade.

Step 4
Butter bread. Grill, buttered side down, for 2 minutes. Place cheese on bottom halves, and bake in oven until melted.

Step 5
Slice steak thinly, against the grain. Top cheese with pickle, steak, onion, and bread. Halve each sandwich, and serve.

Source: https://www.marthastewart.com/317057/marinated-flank-steak-sandwiches