In a small bowl, combine the smoked paprika, garlic powder, onion powder, thyme, oregano, cayenne, sea salt, and black pepper.
Pat the catfish fillets dry with a paper towel and coat both sides generously with the spice mixture.
In another small bowl, whisk together the Greek yogurt, Dijon mustard, minced capers, and lemon juice to create the remoulade.
Heat the avocado oil in a large cast-iron skillet over medium-high heat until shimmering.
Carefully place the catfish in the skillet and sear for 3-4 minutes per side until the crust is dark and the fish flakes easily with a fork.
While the fish cooks, steam or lightly sauté the green beans until tender-crisp.
Serve the blackened catfish immediately with a dollop of the zesty remoulade and the green beans on the side.