Dice capsicum and potato. Finely chop 2 onions and roughly chop 1 onion, tomato and green chillies. Grind it to a smooth paste along with cashewnuts without adding water.
Heat 2 tbsp oil in a skillet and fry green bell peppers for 2-3 minutes on medium heat. Set aside.
To the same skillet add 1 tbsp oil and add chopped onions. Fry till translucent.
Add ginger garlic paste and saute for about 1 minute.
Add 1/4 cup water and add chilli powder, coriander powder, cumin powder and turmeric powder. Saute till the raw smell is lost.
Add the ground onion paste and saute for about 3 minutes.
Add potatoes, mix well, cover and cook till the potatoes are soft.
Add Green bell pepper along with garam masala powder and amchur. Mix it well. (If the curry is too dry, add 1/2 a cup of water)
Cover and cook for further 3 minutes.
Serve hot.