Slice the russet potato into thin wedges and soak in cold water for 10 minutes to remove excess starch, then pat completely dry.
Toss the potato wedges with half of the avocado oil and a pinch of sea salt, then air-fry at 400°F for 15-20 minutes until golden and crispy.
In a small mixing bowl, whisk together the arrowroot powder, garlic powder, paprika, sea salt, and black pepper.
Slowly pour the light beer into the dry mixture, whisking until a smooth, thin batter forms.
Pat the cod fillets very dry with paper towels to ensure the batter adheres properly.
Heat the remaining avocado oil in a non-stick skillet over medium-high heat until shimmering.
Dip each cod fillet into the beer batter, allowing the excess to drip off, then carefully place into the hot skillet.
Sear the fish for 3-4 minutes per side until the coating is crisp and the fish flakes easily with a fork.
Serve the hot battered cod immediately alongside the crispy potato chips with a fresh lemon wedge.