Heat a pan over moderate flame.
Add some water to the pan.
Put the liver in along with ginger garlic paste and cinnamon stick.
Boil for 6 to 9 minutes.
Remove liver pieces, wash and keep aside.
Reserve the stock.
In a small bowl, mix the green chillies, peppercorns, cumin, vinegar, sugar and salt.
Apply this on the liver pieces and keep aside to marinate for 5 to 10 minutes.
Heat ghee in a pan.
Saute the onions till golden brown.
Add salt, marinated liver pieces with the marinade.
Pour the reserved stock and bring to a boil.
Add the tomatoes and cook all water has dried up.
Remove and transfer to a serving bowl.
Serve hot with rice or chapati.