Preheat your air fryer to 400°F (200°C).
Slice the Russet potato into even wedges, toss with half of the avocado oil, a pinch of sea salt, and black pepper.
Place the potato wedges in the air fryer basket and cook for 15-20 minutes, shaking halfway through, until golden and crisp.
While potatoes cook, pat the cod fillet completely dry with a paper towel and season with smoked paprika and remaining salt and pepper.
In a small bowl, whisk together the arrowroot powder and light beer until a smooth, thin batter forms.
Dip the cod fillet into the batter, ensuring it is fully coated, and spray the air fryer rack with the remaining avocado oil.
Place the battered fish in the air fryer (next to the potatoes if space allows, or after they are done) and cook at 375°F for 10-12 minutes until the coating is set and the fish flakes easily.
In a small ramekin, mix the Greek yogurt, lemon juice, and chopped capers to create a clean tartar sauce.
Serve the crispy fish immediately alongside the potato wedges with the tartar sauce on the side.