Pat the sirloin steak dry with paper towels and cut into 1-inch cubes, then trim the woody ends off the asparagus and cut into 2-inch pieces.
Heat a large cast-iron skillet over medium-high heat and add the ghee, allowing it to melt and coat the pan evenly.
Add the steak bites in a single layer, seasoning with sea salt, black pepper, and dried thyme, and sear for 2 minutes until a golden-brown crust forms.
Flip the steak and add the asparagus pieces to the skillet, sautéing for another 3-4 minutes until the steak is cooked through and asparagus is vibrant.
Reduce the heat to medium, stir in the minced garlic, and cook for 1 minute until highly aromatic without burning the garlic.
Remove from heat, drizzle with fresh lemon juice, and toss everything together to glaze before serving.