Preheat your oven to 250°F and place a wire cooling rack over a rimmed baking sheet.
Pat the ribeye steak completely dry with paper towels and season all sides with sea salt and black pepper.
Place the steak on the wire rack and roast in the oven until the internal temperature reaches 115-120°F for medium-rare, which usually takes 45 to 60 minutes.
While the steak roasts, peel the russet potato and cut it into 1/2-inch thick batons.
Submerge the potato fries in a bowl of ice-cold water for 15 minutes to remove excess starch, then drain and pat very dry.
Toss the dried potatoes with avocado oil and a pinch of salt, then place them in the air fryer basket.
Air fry the potatoes at 375°F for 18-20 minutes, shaking the basket halfway through, until the exteriors are golden and crisp.
In a small ramekin, mash the grass-fed butter with minced garlic, finely chopped parsley, and dried thyme to create the herb compound butter.
Heat a cast-iron skillet over high heat until smoking; sear the roasted steak for 60 seconds per side to develop a deep brown crust.
Remove the steak from the pan, top with the garlic herb butter, and allow it to rest for 5-8 minutes before slicing and serving with the hot frites.