Pat the salmon fillet completely dry with a paper towel and season both sides with the sea salt, black pepper, and garlic powder.
Heat the avocado oil in a medium cast-iron or stainless steel skillet over medium-high heat until the oil is shimmering and hot.
Carefully place the salmon in the pan, skin-side up, and sear for 4 to 5 minutes without moving it to develop a golden-brown crust.
Flip the salmon fillet and add the trimmed asparagus spears to the pan, arranging them around the fish.
Sauté the asparagus for 4 to 6 minutes while the salmon finishes cooking, until the fish is opaque and the vegetables are crisp-tender.
While the salmon rests for a minute, whisk together the Greek yogurt, lemon juice, and chopped fresh dill in a small bowl.
Plate the salmon and asparagus, then finish the dish by drizzling the creamy lemon-dill sauce over the top.