Coat the cubed tofu with cornflour and set aside.
Heat oil in a pan and fry the tofu until golden brown. Remove and set aside.
In the same pan, add sliced onions and sauté until translucent.
Add sliced capsicum and green chillies, and cook for a few minutes.
Stir in ginger-garlic paste and sauté until fragrant.
Add soy sauce, tomato ketchup, vinegar, and salt; mix well.
Return the fried tofu to the pan and toss to coat well.
Cook for a couple of minutes, then garnish with chopped coriander leaves before serving.