Pat the catfish fillets completely dry with a paper towel to ensure the spices adhere and create a crispy crust.
In a small bowl, mix the smoked paprika, garlic powder, onion powder, dried thyme, cayenne pepper, sea salt, and black pepper.
Generously coat both sides of the catfish fillets with the spice mixture, pressing it into the flesh.
Prepare the remoulade by whisking together the Greek yogurt, Dijon mustard, lemon juice, and finely chopped capers in a small ramekin.
Heat the avocado oil in a cast-iron skillet over medium-high heat until it begins to shimmer.
Carefully place the catfish in the hot skillet and sear for 3-4 minutes per side until the spice crust is blackened and the fish is opaque and flaky.
While the fish cooks, steam the green beans for 5 minutes until they are tender-crisp and bright green.
Serve the blackened catfish immediately with a dollop of the zesty remoulade and the steamed green beans on the side.