Preheat your oven to 400°F and line a baking sheet with parchment paper.
Peel the sweet potato and cut it into uniform 1/2-inch cubes.
Toss the sweet potato cubes with olive oil and half of the salt and pepper directly on the baking sheet.
Roast for 20-25 minutes, tossing halfway through, until the potatoes are golden and tender.
While the potatoes roast, pat the steak dry with paper towels and season both sides with the remaining salt and pepper.
Heat a cast-iron skillet over medium-high heat until it is very hot and slightly smoking.
Place the steak in the skillet and sear for 3-4 minutes per side for a perfect medium-rare.
In the final 2 minutes of searing, add the ghee, smashed garlic cloves, rosemary, and thyme to the pan.
Tilt the pan slightly and use a large spoon to continuously baste the steak with the melted herb-infused ghee.
Remove the steak from the skillet and let it rest on a cutting board for at least 5 minutes to lock in the juices.
Slice the steak against the grain and serve immediately alongside the roasted sweet potatoes.