Open-Face Steak Bagel Sandwich with Parmesan Dressing – Country Harvest

Ingredients

• 4 Bagel
• 1½ lbs. flank steak
• 1 tbsp. vegetable oil
• ½ small red onion, thinly sliced
• ¼ cup whole grain mustard
• 3 tbsp. fresh lemon juice
• ½ cup olive oil, plus more for bread
• 1½ oz. Parmesan, finely grated
• 6 cups mature arugula leaves with tender stems
• Kosher salt, freshly ground pepper to taste