- 2 thick slices crusty bread, torn into bite-size pieces (2 cups)
- 3 tablespoons extra-virgin olive oil
- 2 tablespoons grated Parmesan
- Coarse salt and ground pepper
- 1 pound skirt steak, cut into 4 pieces
- 1 red onion, cut crosswise into 1/2-inch-thick rounds
- 1 teaspoon Dijon mustard
- 1 tablespoon balsamic vinegar
- 5 ounces baby or wild arugula
Preheat oven to 400 degrees. On a rimmed baking sheet, toss bread with 2 teaspoons oil and Parmesan, then season with salt and pepper. Bake until golden brown, 7 minutes.
Heat a grill pan or cast-iron skillet over medium-high. Season steak with salt and pepper. Drizzle onions with 1 teaspoon oil and season with salt and pepper. Grill steak and onions until steak is medium-rare and onions are tender, 5 to 7 minutes, flipping once. Let steak rest 5 minutes before thinly slicing against the grain.
Meanwhile, in a large bowl, whisk together mustard, vinegar, and 2 tablespoons oil. Add arugula and season with salt and pepper. Add onions, steak, and croutons and toss to combine. Serve immediately.