Preheat your oven to 400°F (200°C).
Peel the sweet potato and cut it into uniform 1/2-inch cubes.
On a large rimmed baking sheet, toss the sweet potato cubes with avocado oil, smoked paprika, and a pinch of sea salt.
Spread the potatoes in a single layer and roast for 20-25 minutes, flipping halfway through, until edges are caramelized and tender.
While potatoes roast, season the sirloin steak on both sides with garlic powder, sea salt, and black pepper.
Heat a cast-iron skillet over medium-high heat and add the ghee, swirling to coat the pan.
Once the pan is shimmering, sear the steak for 4-5 minutes per side for medium-rare, or until it reaches your preferred internal temperature.
Remove the steak from the skillet and place it on a cutting board to rest for at least 5 minutes before slicing.
In the same skillet, add the broccolini with a splash of water; cover and steam-sauté for 3-4 minutes until bright green and tender-crisp.
Slice the steak against the grain and serve alongside the roasted sweet potatoes and steamed broccolini.