Preheat your oven to 400°F and line a baking sheet with parchment paper.
Toss the green beans with olive oil and a pinch of sea salt on the baking sheet, then roast for 15-18 minutes until tender and slightly charred.
In a small bowl, whisk together the Greek yogurt, lemon juice, minced garlic, and chopped parsley to create the aioli, then set aside.
In a separate shallow dish, combine the smoked paprika, thyme, oregano, garlic powder, onion powder, cayenne, sea salt, and black pepper.
Pat the catfish fillets completely dry with paper towels and coat both sides generously with the spice mixture.
Heat the ghee in a cast-iron skillet over medium-high heat until it is shimmering and very hot.
Place the catfish in the skillet and sear for 3-4 minutes per side until the crust is dark and blackened and the fish flakes easily with a fork.
Serve the blackened catfish immediately alongside the roasted green beans with a dollop of the lemon aioli on top.