Preheat oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a small bowl, whisk together the smoked paprika, garlic powder, onion powder, thyme, oregano, cayenne, 0.25 tsp sea salt, and black pepper.
Pat the salmon fillet dry with a paper towel and rub the spice mixture evenly over all sides of the fish.
Toss the asparagus spears with olive oil and 0.125 tsp sea salt on the prepared baking sheet.
Roast the asparagus for 10-12 minutes until the tips are slightly charred and the stalks are tender.
While asparagus roasts, heat avocado oil in a cast-iron skillet over medium-high heat.
Place salmon skin-side up in the skillet and sear for 3-4 minutes until a dark, smoky crust forms.
Flip the salmon and cook for another 3-4 minutes until the fish flakes easily with a fork.
Plate the blackened salmon alongside the roasted asparagus and serve immediately.