Preheat your oven to 425°F and line a large baking sheet with parchment paper.
Slice the potato into thin wedges, toss them in a bowl with the avocado oil and a pinch of sea salt, then spread them in a single layer on the baking sheet.
Roast the potatoes for 15 minutes while you prepare the fish.
Pat the cod fillets completely dry with a paper towel and season both sides with sea salt, black pepper, garlic powder, and paprika.
In a shallow dish, whisk together the gluten-free flour and light beer until a smooth, thin batter forms.
Remove the baking sheet from the oven, flip the potatoes, and move them to one side to make room for the fish.
Dip each cod fillet into the beer batter, letting the excess drip off, and place them onto the hot baking sheet.
Return the tray to the oven and bake for another 12 to 15 minutes, or until the fish is opaque and the batter is set and crispy.
Serve the fish and chips immediately with a fresh lemon wedge squeezed over the top.