In a small bowl, combine smoked paprika, garlic powder, onion powder, salt, and black pepper. Rub the spice mixture over the flat iron steak, ensuring it is evenly coated. Drizzle with olive oil and let marinate for at least 30 minutes at room temperature or up to overnight in the refrigerator.

Preheat the oven to 425°F (220°C). In a large bowl, toss the cut potatoes with olive oil, Cajun seasoning, and salt until evenly coated. Spread the fries in a single layer on a baking sheet lined with parchment paper. Bake in the preheated oven for 25-30 minutes, flipping halfway through, until golden and crispy.

Preheat a grill or grill pan over medium-high heat. Once hot, add the marinated steak and cook for 4-5 minutes on each side for medium-rare, or until your desired doneness is reached. Remove from heat and let rest for 5 minutes before slicing against the grain.

In a small bowl, combine mayonnaise, minced chipotle in adobo, garlic, lime juice, and season with salt and pepper to taste. Mix well and set aside.

Slice the flat iron steak and serve alongside the Cajun-spiced fries. Drizzle the zesty chipotle garlic sauce over the steak or serve on the side for dipping.