Preheat your air fryer to 400°F to ensure a hot start for the potatoes.
Cut the russet potato into even wedges and toss them in a bowl with the avocado oil and a pinch of sea salt.
Place the wedges in the air fryer basket and cook for 15 minutes, shaking halfway through, until they are tender inside and browned on the edges.
While the potatoes cook, pat the cod fillets completely dry with paper towels to ensure the batter sticks properly.
In a shallow bowl, whisk together the flour, baking powder, garlic powder, sea salt, black pepper, and cold light beer until the batter is smooth and airy.
Dip each piece of cod into the batter, allowing any excess to drip off, then place them in the air fryer basket once the potatoes are removed.
Air fry the fish at 375°F for 10 to 12 minutes until the coating is shattered-crisp and the fish is opaque throughout.
Serve the hot fish and chips immediately with a fresh lemon wedge squeezed over the top for a bright finish.