Start by bringing the ribeye steak to room temperature for about 30 minutes.
Preheat your oven to 400°F (200°C).
Season both sides of the steak generously with salt and pepper.
Heat olive oil in a skillet over medium-high heat until shimmering.
Add the steak and sear for 3-4 minutes on each side until a crust forms.
Add minced garlic and rosemary to the pan, spooning oil over the steak.
Transfer the skillet to the oven and roast for 5-7 minutes for medium-rare.
Meanwhile, boil the halved potatoes in salted water until tender, about 15 minutes.
Drain the potatoes, then toss them in olive oil, salt, and pepper before roasting in the oven for 20 minutes.
In a separate pan, sauté spinach in butter until wilted, about 2-3 minutes.
Remove steak from the oven, let it rest for 5 minutes before slicing.
Serve the sliced steak with roasted potatoes and sautéed spinach.