Marinade chicken with ½ teaspoon salt, ½ teaspoon black pepper powder, ½ teaspoon red chili powder and 2 tea spoons soya sauce for 30 minutes.
Heat 2 tbsp oil in pan and fry chicken until soft. Remove in a plate.
Add 2 tea spoons oil in same pan. Add minced garlic and sauté until gives an aroma. Now add tamarind juice, salt, vinegar, hot sauce, sugar, remaining black pepper powder, and red chili powder and ketchup. Stir well.

When it starts bubble, add water according to the thick gravy you want. Cook it for 2 minutes.
Then add cube capsicum and onion; cook for 5 minutes or until half cook.
Now add chicken and cook until vegetables are done.
If you want thick gravy add corn flour paste.

Dish it out and serve with chicken fried rice.