In a small bowl, mix together garlic powder, smoked paprika, salt, black pepper, chili flakes, and Worcestershire sauce until well combined.

Rub 1 tablespoon of olive oil over the flank or sirloin steak, then coat thoroughly with the seasoning mixture. Let it marinate for at least 10 minutes.

Heat a skillet over medium-high heat and add another tablespoon of olive oil. Add sliced onions and green bell peppers and sauté for about 7-8 minutes until soft.

Remove the veggies and set them aside. In the same skillet, add the marinated steak and cook for 3-4 minutes per side.

After cooking, let the steak rest for 5 minutes, then slice thinly against the grain.

Spread mayonnaise and Dijon mustard on the sandwich rolls or hoagie buns.

Layer the sliced steak, sautéed veggies, and cheese on the rolls. Optionally broil for 1-2 minutes to melt the cheese.

Add fresh arugula or lettuce, close the sandwiches, and serve.