Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Peel the sweet potato and cut it into 1/2-inch cubes to ensure even roasting.
In a medium bowl, toss the sweet potato cubes with 0.5 tbsp of olive oil, dried rosemary, and a pinch of salt and pepper.
Spread the potatoes in a single layer on the baking sheet and roast for 20-25 minutes until they are golden and crispy.
While the potatoes roast, pat the steak dry with a paper towel and season both sides with garlic powder and the remaining salt and pepper.
Heat the remaining 0.5 tbsp of olive oil in a cast-iron skillet over medium-high heat until shimmering.
Sear the steak for 3-4 minutes per side for medium-rare, or until it reaches your desired level of doneness.
Remove the steak from the pan and let it rest on a cutting board for 5 minutes before slicing it against the grain.
Place the fresh spinach on a plate and top with the sliced steak and crispy sweet potatoes, allowing the heat to wilt the greens slightly.