Cut the Russet potato into thick wedges and soak them in a bowl of cold water for 10 minutes to remove excess starch.
Drain and thoroughly pat the potato wedges dry with a clean kitchen towel.
Toss the potatoes with half of the avocado oil and a pinch of sea salt, then place them in the air fryer basket at 400°F for 15-20 minutes until golden and crisp.
In a small bowl, whisk together the spelt flour, light beer, garlic powder, paprika, sea salt, and black pepper until a smooth batter forms.
Pat the cod fillet dry with paper towels and dip it into the batter, ensuring it is evenly coated on all sides.
Lightly brush the remaining avocado oil onto the air fryer tray or a non-stick pan; cook the fish at 375°F for 10-12 minutes, flipping halfway through, until the coating is crispy and the fish flakes easily.
Serve the beer-battered fish immediately with the thick-cut chips and a fresh lemon wedge for squeezing.