In a small bowl, whisk together the smoked paprika, garlic powder, onion powder, dried thyme, dried oregano, cayenne pepper, sea salt, and black pepper.
Pat the catfish fillets completely dry with a paper towel, then coat both sides evenly with the spice rub, pressing it into the flesh.
Prepare the tartar sauce by combining the Greek yogurt, finely minced dill pickles, Dijon mustard, and lemon juice in a small ramekin; set aside in the refrigerator.
Steam the trimmed green beans for 5-6 minutes until they are bright green and crisp-tender.
Heat the avocado oil in a large cast-iron skillet over medium-high heat until it begins to shimmer.
Carefully place the seasoned catfish into the hot skillet and sear for 3-4 minutes per side until a dark crust forms and the fish flakes easily with a fork.
Serve the blackened catfish immediately alongside the steamed green beans and a generous dollop of the yogurt tartar sauce.