Peel and grate the bottle gourd. Mix half-teaspoon salt and keep aside for fifteen minutes. Squeeze to remove excess water. Add besan, red chilli powder and mix to make dough. Divide it into ten to twelve equal portions.
Stuff one-piece tamarind into each portion of this mixture. Wet your palm and shape the stuffed portion into a ball. Heat oil in a kadai and deep-fry the prepared koftas, in small batches for two to three minutes or until golden brown in colour and crisp from the outside.
Drain and remove onto an absorbent paper. Peel and finely chop onions. Clean and remove stems from dry red chillies. Peel ginger, garlic and grind to a fine paste along with dry red chillies. Wash and puree tomatoes in a blender.
Clean, wash and finely chop fresh coriander leaves. Heat oil in a pan, add chopped onions and sauté until light golden brown. Add ginger, garlic and red chilli paste, stir-fry briefly. Add turmeric powder, coriander powder, cumin powder and red chilli powder.
Continue to cook on medium heat for one minute, stirring continuously Stir in tomato puree and cook on high heat, stirring continuously till oil begins to separate. Add two cups of water and bring it to a boil.
Add salt, reduce heat and simmer for five minutes. Gently add the fried koftas and simmer for another three to four minutes. Sprinkle garam masala powder and serve garnished with chopped fresh coriander leaves.