Prep the veggies: Wash, dry well, and cut into even pieces. Keep florets small, slice sweet potatoes thin (about 1/8 inch), and pat everything dry so the batter sticks.

Preheat the air fryer: Set to 390–400°F (200–205°C) for at least 5 minutes. A hot air fryer helps instant crisping.

Mix the dry ingredients: In a large bowl, whisk 3/4 cup all-purpose flour, 1/2 cup cornstarch, 1 teaspoon baking powder, 1/2 teaspoon kosher salt, and a pinch of garlic/onion powder if using.

Make the batter: Pour in 1 cup ice-cold sparkling water. If using an egg, whisk it lightly first and add now. Stir gently with chopsticks or a fork just until combined. Small lumps are fine. Do not overmix.

Keep it cold: Set the batter bowl over another bowl with ice, or pop it in the fridge between batches. Cold batter equals lighter tempura.

Coat the veggies: Working in batches, toss a handful of vegetables into the batter. Let excess drip off. For extra crispness on wetter veggies (like mushrooms), dust lightly with cornstarch before dipping.

Prep the basket: Lightly spray the air fryer basket with oil to reduce sticking.

Arrange and spray: Place battered veggies in a single layer without crowding. Lightly mist the tops with oil spray. This helps the batter turn golden.

Air fry: Cook for 7–10 minutes, flipping halfway and lightly spraying again. Time varies by veggie and size. You’re aiming for pale golden and crisp.

Batch and keep warm: Transfer finished pieces to a wire rack. Keep them warm in a low oven (200°F/95°C) while you finish the rest.

Make a quick dipping sauce: Stir together 2 tablespoons soy sauce, 1 tablespoon rice vinegar, a pinch of sugar, and a splash of water. Add grated ginger or a touch of chili oil if you like.

Serve right away: Tempura is best hot and fresh. Sprinkle with a little salt and serve with dipping sauce and lemon wedges.