Preheat your air fryer to 400°F (200°C) to ensure a high-heat environment for maximum crispiness.
Slice the russet potato into even wedges, then toss them in a bowl with 0.5 tbsp of avocado oil and half of the salt and pepper.
Arrange the potato wedges in a single layer in the air fryer basket and cook for 15-18 minutes, shaking the basket halfway through.
While the fries cook, whisk together the flour, light beer, garlic powder, and paprika in a shallow bowl until the batter is smooth and aerated.
Pat the cod fillets completely dry with a paper towel and season both sides with the remaining salt and pepper.
Dip each fillet into the beer batter, allowing the excess to drip off, then lightly mist or brush the fish with the remaining avocado oil.
Move the fries to one side of the basket and place the fish in the other side, air frying for an additional 10-12 minutes until the coating is golden-brown.
Serve the fish and fries immediately with a fresh squeeze of lemon for a bright, zesty finish.