STEAK SANDWICHES WITH CARAMELIZED SWEET ONIONS

Steak Sandwiches with Caramelized Sweet Onions image

Provided by Martha Stewart

Number Of Ingredients 12

1 tablespoon whole black peppercorns
1 tablespoon whole white peppercorns
1 tablespoon whole coriander seeds
1 teaspoon brown mustard seeds
1 New York strip steak (about 1 pound; 3/4 to 1 1/4 inches thick)
4 garlic cloves
1/2 cup plus 2 tablespoons plus 1 teaspoon extra-virgin olive oil
1 Vidalia onion, halved and cut into 1/4-inch-thick slices
Coarse salt
4 ciabatta rolls, halved horizontally
1/2 teaspoon fresh lemon juice
1 ounce baby arugula

Steps:

Coarsely grind together the spices in a spice grinder, then rub steak all over with spice mixture. Refrigerate 30 minutes.
Blend garlic and 1/2 cup oil in a blender until combined. Set garlic oil aside.
Heat 2 tablespoons olive oil in a medium skillet over medium heat. Add onion, and cook, stirring occasionally, until caramelized, about 25 minutes.
Bring steak to room temperature. Preheat grill to medium (if using a charcoal grill, coals are ready when you can hold your hand 5 inches above grill for just 5 or 6 seconds). Season steak with salt. Grill, flipping once, until medium-rare, about 8 minutes per side. Let rest 10 minutes.
Brush cut sides of rolls with garlic oil to taste. Grill rolls, cut sides down, until slightly charred around edges.
Whisk remaining teaspoon olive oil, the lemon juice, and a pinch of salt in a small bowl. Add arugula; toss to combine.
Thinly slice steak at an angle. Divide steak, onion, and arugula among rolls.