Pat the catfish fillets completely dry with paper towels to ensure a crisp sear.
In a small bowl, combine the smoked paprika, garlic powder, onion powder, thyme, oregano, cayenne, salt, and pepper.
Press the spice mixture firmly onto both sides of the catfish fillets until they are evenly coated.
Heat the avocado oil in a cast-iron skillet over medium-high heat until it begins to shimmer.
Carefully place the catfish in the skillet and cook for 3-4 minutes per side until the crust is dark and the fish flakes easily with a fork.
While the fish cooks, whisk together the Greek yogurt, lemon juice, and lemon zest in a small ramekin to create the aioli.
Steam the asparagus spears for 4-5 minutes until they are bright green and tender-crisp.
Plate the blackened catfish alongside the steamed asparagus and serve with a dollop of the lemon aioli.