In a small bowl, combine the smoked paprika, garlic powder, onion powder, dried thyme, dried oregano, cayenne pepper, sea salt, and black pepper to create the blackening seasoning.
Pat the catfish fillet completely dry with paper towels, then coat both sides generously with the spice mixture, pressing it into the flesh.
Heat a cast-iron skillet over medium-high heat and add half of the avocado oil.
Place the seasoned catfish in the hot skillet and sear for 3 to 4 minutes per side until the crust is dark and the fish flakes easily with a fork.
Remove the fish from the pan and set aside to rest.
In the same skillet, add the remaining avocado oil along with the sliced bell peppers and red onion.
Sauté the vegetables for 5 minutes until they are tender-crisp and slightly charred.
Serve the blackened catfish over the sautéed vegetables and garnish with freshly chopped parsley.