Pat the salmon fillet completely dry with a paper towel to ensure a proper sear.
In a small bowl, whisk together the smoked paprika, garlic powder, onion powder, sea salt, and black pepper.
Rub the spice mixture evenly over both sides of the salmon fillet, pressing gently so the seasoning adheres.
Trim the woody ends off the asparagus spears and toss them with the lemon zest and a pinch of salt.
Heat the olive oil in a large cast-iron or stainless steel skillet over medium-high heat until shimmering.
Place the salmon in the skillet skin-side up and cook for 4 minutes until a dark, flavorful crust forms.
Flip the salmon and add the asparagus spears to the empty spaces in the pan.
Cook for another 3 to 4 minutes until the salmon is opaque and the asparagus is tender yet still has a snap.
Drizzle the lemon juice over both the salmon and asparagus just before removing from the heat.
Serve immediately while the salmon is hot and the asparagus is bright green.