In a small bowl, whisk together the smoked paprika, garlic powder, onion powder, oregano, thyme, cayenne, sea salt, and black pepper.
Pat the catfish fillets completely dry with a paper towel and coat both sides generously with the spice rub.
In another small bowl, combine the Greek yogurt, Dijon mustard, lemon juice, hot sauce, and chopped parsley to create the remoulade.
Heat the avocado oil in a large cast-iron skillet over medium-high heat until it is shimmering and very hot.
Place the catfish fillets in the skillet and sear for 3 to 4 minutes per side until the crust is dark and the fish flakes easily with a fork.
While the fish cooks, steam the green beans for 5 minutes until they are bright green and tender-crisp.
Plate the blackened catfish alongside the green beans and serve with a dollop of the Cajun remoulade.