In a small bowl, whisk together the smoked paprika, garlic powder, onion powder, oregano, thyme, cayenne pepper, sea salt, and black pepper to create the blackened seasoning.
Pat the catfish fillets completely dry with a paper towel and coat both sides generously with the spice rub, pressing it into the flesh.
In another small bowl, combine the Greek yogurt, lemon juice, and minced garlic to create the aioli; set aside.
Heat the avocado oil in a large cast-iron skillet over medium-high heat until it begins to shimmer.
Place the catfish in the skillet and sear for 3-4 minutes per side until the spice crust is dark and the fish flakes easily with a fork.
While the fish cooks, steam the broccoli florets for 4-5 minutes until they are tender and bright green.
Plate the blackened catfish alongside the steamed broccoli and top the fish with a dollop of the lemon aioli.