• Core, then cut pepper into 1/2-inch slices.
• Halve buns. 
• Pat steaks dry with paper towels. Sprinkle half the Italian Seasoning (use all for 4 portions) all over steaks, then season with salt and pepper. Set aside.

• Heat a large non-stick pan over medium-high.
• When hot, add 1 tbsp (2 tbsp) oil, then onions and peppers. Cook, stirring occasionally, until tender-crisp, 3-4 min. Season with salt and pepper.
• Transfer veggies to a plate.

• Add 1/2 tbsp (1 tbsp) oil, then steaks to the same pan. Sear until golden-brown, 1-2 min per side. Don't crowd the pan; work in batches, if necessary.
• Remove the pan from heat, then transfer steaks to a foil-lined baking sheet.
• Broil in the middle of the oven until cooked to desired doneness, 4-7 min.**

• Meanwhile, whisk together half the balsamic glaze and 1 tbsp (2 tbsp) oil in a large bowl.

• Thinly slice steaks.
• Remove foil from the baking sheet (from step 3), then arrange buns on the unlined sheet, cut-side up.
• Spread mayo over buns.
• Stack steak on bottom buns, then drizzle with remaining balsamic glaze.
• Arrange half the veggies on top, then sprinkle cheese over veggies.
• Broil in the middle of the oven until cheese melts, 1-2 min. (TIP:  Keep an eye on them so they don't burn.) 

• Meanwhile, add spring mix and remaining veggies to the bowl with dressing. Season with salt and pepper, then toss to combine.
• When cheese is melted, close sandwiches with top buns.
• Divide sandwiches and salad between plates.

If you've opted for double striploin steak, prep and cook in the same way the recipe instructs you to prep and cook the regular portion of sirloin steak. Work in batches if necessary.