In a small bowl, combine the smoked paprika, garlic powder, onion powder, dried thyme, dried oregano, sea salt, black pepper, and cayenne pepper to create the Cajun rub.
Pat the catfish fillets completely dry with paper towels to ensure a crispy sear, then generously coat both sides of the fish with the spice mixture.
Place a cast-iron skillet over medium-high heat and add the avocado oil, swirling to coat the bottom of the pan.
Once the oil is shimmering and hot, carefully place the catfish fillets in the skillet and sear for 3 to 4 minutes per side until the crust is blackened and the fish flakes easily with a fork.
While the fish cooks, steam the green beans in a small amount of water for 4 to 5 minutes until they are bright green and crisp-tender.
Warm the pre-cooked quinoa in a separate pan or microwave until heated through.
Plate the blackened catfish alongside the quinoa and green beans, serving immediately with a fresh lemon wedge for squeezing over the fish.