Preheat the air fryer to 400°F (200°C).
In a bowl, combine all-purpose flour, corn flour, Kashmiri red chili powder, salt, ginger paste, garlic paste, and enough water to make a thick batter.
Dip each cauliflower floret into the batter, ensuring they are well-coated. Place them in the air fryer basket, ensuring they are not touching each other.
Spray the coated cauliflower with oil. Air fry for 12 minutes at 400°F, flipping the florets halfway through to ensure even cooking. The gobi should be crispy and golden brown.
While the gobi is air frying, prepare the sauce. In a bowl, mix soy sauce, tomato ketchup, red chili sauce, vinegar, corn starch, black pepper powder, and water. Stir well to form a smooth sauce.
Heat oil in a pan over medium heat. Add diced onions, bell peppers, white part of the green onions, and slit green chili. Sauté until the vegetables are slightly tender but still crisp.
Pour the prepared sauce into the pan and stir continuously until the sauce thickens and coats the vegetables evenly.
Add the air-fried gobi to the pan, tossing gently to coat the cauliflower in the sauce.
Garnish with chopped green onions (green part) and serve hot.