Pat the sirloin steak dry with paper towels and season both sides evenly with sea salt and black pepper.
Heat the avocado oil in a cast-iron skillet over medium-high heat until it begins to shimmer.
Carefully place the steak in the hot skillet and sear for 3 to 4 minutes per side for medium-rare doneness.
During the final 2 minutes of searing, add the grass-fed butter, minced garlic, rosemary, and thyme to the pan.
Tilt the skillet slightly and use a spoon to continuously baste the steak with the melted herb butter.
Transfer the steak to a clean cutting board and let it rest for 5 minutes to lock in the juices.
In the same skillet with the remaining pan juices, add the asparagus spears and cherry tomatoes.
Sauté the vegetables for 4 to 5 minutes until the asparagus is crisp-tender and the tomatoes begin to burst.
Slice the steak against the grain and serve immediately alongside the warm sautéed vegetables.