Use a paper towel to pat the trout fillets completely dry to ensure the skin gets maximum crispiness.
Season both sides of the trout evenly with the sea salt, black pepper, and garlic powder.
Heat the ghee in a large cast-iron or stainless steel skillet over medium-high heat until it is shimmering.
Place the trout fillets in the pan skin-side down, pressing down lightly with a spatula for 10 seconds to prevent curling.
Sear the fish for 3 to 4 minutes without moving it, then carefully flip and cook for an additional 1 to 2 minutes until just opaque.
Remove the trout from the pan and add the asparagus spears, sautéing them in the remaining fat for 4 minutes until tender-crisp.
In a small bowl, whisk together the Greek yogurt, fresh dill, and lemon juice until the sauce is smooth and creamy.
Plate the trout over the sautéed asparagus and drizzle generously with the lemon-dill sauce before serving.