Mix red chili powder with 1 tbsp water to form a quick chili paste.
Dust target protein cubes or vegetables with cornstarch, salt, and pepper; shallow-fry in 1 tbsp oil until golden crisp.
Heat remaining oil in a wok on high flame, sauté garlic paste and chili paste for 30 seconds.
Add diced capsicum and onion squares; stir-fry rapidly for 2 minutes.
Add soy sauce, vinegar, and fried cubes; toss continuously for 1 minute and serve hot.