In a small bowl, whisk together the smoked paprika, garlic powder, onion powder, dried thyme, dried oregano, cayenne pepper, sea salt, and black pepper to create the blackening spice.
Pat the catfish fillet completely dry with paper towels and coat both sides evenly with the spice mixture, pressing it gently into the flesh.
Heat the ghee in a cast iron skillet over medium-high heat until it is shimmering and very hot.
Carefully place the catfish in the skillet and sear for 3 to 4 minutes per side until the crust is dark and charred and the fish flakes easily with a fork.
While the fish cooks, whisk the Greek yogurt, Dijon mustard, lemon juice, and capers in a small bowl to create the zesty remoulade.
Steam the green beans in a small amount of water for 4 to 5 minutes until they are bright green and tender-crisp.
Plate the blackened catfish alongside the steamed green beans and top with a generous dollop of the remoulade.