Pat the catfish fillets dry with a paper towel to ensure a perfect, crusty sear.
In a small bowl, combine smoked paprika, garlic powder, onion powder, oregano, thyme, cayenne, salt, and pepper to create the blackening seasoning.
Coat both sides of the catfish generously with the spice rub, pressing it firmly into the flesh.
Heat avocado oil in a cast-iron skillet over medium-high heat until shimmering.
Place the catfish in the hot 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, whisk together the Greek yogurt, Dijon mustard, lemon juice, and chopped capers in a small bowl to make the remoulade.
Steam or lightly sauté the green beans in a separate pan until they are bright green and tender-crisp.
Serve the blackened catfish immediately with a dollop of the tangy remoulade and the green beans on the side.