Preheat your air fryer to 400°F (200°C).
Slice the russet potato into thin wedges and toss them in a bowl with the avocado oil and a pinch of sea salt.
Place the potato wedges in the air fryer basket in a single layer and cook for 15-18 minutes, shaking halfway through, until crispy.
While the potatoes cook, whisk together the cassava flour, light lager, garlic powder, paprika, and black pepper in a shallow bowl to create a smooth batter.
Pat the cod fillets dry with a paper towel and season lightly with sea salt.
Dip each cod fillet into the batter, ensuring it is fully coated, and let any excess drip off.
Place the battered fish into the air fryer basket and cook at 375°F for 10-12 minutes until the coating is golden and the fish flakes easily.
Serve the hot fish and chips immediately with a fresh lemon wedge for a bright finish.