In a small bowl, whisk together the smoked paprika, onion powder, 0.25 tsp of the garlic powder, cayenne pepper, dried oregano, dried thyme, sea salt, and black pepper to create the blackening seasoning.
Pat the catfish fillets completely dry with paper towels, then coat both sides of the fish generously with the seasoning blend, pressing it in with your fingers.
Prepare the lemon aioli by combining the avocado oil mayonnaise, lemon juice, and the remaining 0.25 tsp of garlic powder in a small ramekin; stir until smooth and set aside.
Heat the ghee in a large cast-iron skillet over medium-high heat until it is very hot and shimmering.
Carefully place the seasoned catfish fillets into the hot skillet and sear for approximately 3 to 4 minutes per side, until a dark crust has formed and the fish flakes easily with a fork.
Remove the catfish from the skillet and set aside to rest. Add the sliced zucchini to the same hot skillet and sauté for 3 to 5 minutes until tender-crisp and slightly browned.
Serve the blackened catfish immediately alongside the sautéed zucchini, topped with a dollop of the lemon aioli.