Pat the steaks dry with a paper towel and season both sides evenly with sea salt, black pepper, and garlic powder.
Dice the russet potato into small, uniform 1/2-inch cubes to ensure they cook quickly and evenly in the pan.
Heat the ghee in a large skillet over medium-high heat until shimmering.
Add the diced potatoes and dried rosemary to the skillet, sautéing for 8-10 minutes until the edges are golden brown and the centers are tender.
Remove the potatoes from the pan and set them aside on a plate.
In the same hot skillet, place the steaks and sear for 3-4 minutes per side for medium-rare, then remove them to a cutting board to rest for 5 minutes.
Lower the heat to medium and pour the beef broth and cracked black peppercorns into the pan, scraping the bottom with a wooden spoon to release the flavorful browned bits.
Add the baby spinach to the pan and toss for 1 minute until just wilted, then return the potatoes to the pan to warm through.
Slice the rested steak against the grain and serve alongside the potatoes and spinach, drizzling the remaining pepper sauce from the pan over the top.