Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Toss the broccoli florets and asparagus spears with half of the avocado oil, salt, and pepper on the baking sheet.
Roast the vegetables for 15-18 minutes until the broccoli edges are slightly crisp and the asparagus is tender.
While vegetables roast, pat the steak completely dry with paper towels and season generously with sea salt and black pepper.
Heat the remaining avocado oil in a cast iron skillet over medium-high heat until shimmering.
Place the steak in the hot skillet and sear for 3-4 minutes per side for medium-rare, or until your desired doneness is reached.
During the last minute of cooking, add the butter, smashed garlic clove, and rosemary sprig to the pan.
Tilt the pan slightly and use a spoon to continuously baste the steak with the melted herb butter.
Remove the steak from the pan and let it rest on a cutting board for 5 minutes before slicing.
Serve the sliced steak alongside the roasted vegetables, drizzling any remaining pan juices over the meat.