Preheat your air fryer to 400°F to ensure a hot cooking environment for the potatoes.
Slice the russet potato into thin, even wedges and toss them in a bowl with the olive oil, half of the sea salt, and half of the garlic powder.
Arrange the potato wedges in a single layer in the air fryer basket and cook for 15-18 minutes, shaking the basket halfway through until they are golden and crisp.
While the potatoes are roasting, whisk together the flour, light beer, remaining sea salt, black pepper, and remaining garlic powder in a shallow dish until a thick, smooth batter forms.
Pat the cod fillets completely dry with a paper towel, then dredge each piece into the beer batter until fully and thickly coated.
Once the potatoes are done, remove them and keep warm; place the battered fish into the air fryer (using a piece of perforated parchment paper to prevent sticking) and cook at 375°F for 10-12 minutes until the crust is set and crunchy.
In a small bowl, stir together the Greek yogurt, lemon juice, and minced capers to create a bright and clean tartar sauce.
Plate the hot, crispy fish alongside the potato wedges and serve immediately with the chilled tartar sauce for dipping.