In a small bowl, whisk together the Greek yogurt, Dijon mustard, 0.5 tbsp of the lemon juice, and hot sauce to create the remoulade, then set aside in the refrigerator.
In another small bowl, combine the smoked paprika, garlic powder, onion powder, dried thyme, dried oregano, cayenne pepper, sea salt, and black pepper to form the blackened seasoning.
Pat the catfish fillets dry with a paper towel and coat both sides evenly with the prepared spice blend, pressing it gently into the flesh.
Heat 1 tsp of olive oil in a large cast-iron skillet over medium-high heat until the oil is shimmering and slightly smoking.
Place the catfish in the skillet and sear for 3-4 minutes per side until the crust is dark and charred and the fish flakes easily with a fork.
While the fish cooks, heat the remaining 1 tsp of olive oil in a separate pan over medium heat and sauté the green beans with the remaining 0.5 tbsp lemon juice for 5 minutes until tender-crisp.
Serve the blackened catfish immediately topped with a dollop of the chilled remoulade and the bright green beans on the side.