Cook the potatoes with salt and keep aside. Make sure you dont overcook it. Crush cumin and pepper. Heat ghee/oil in a pan and add crushed cumin and pepper and curry leaves. After a min, add chilli and turmeric powder. Mix well. Add lemon juice, salt (if required) and 2 tbsp water. Mix well. Add cooked potatoes and combine everything. Cook for 5-7 mins on low flame. Serve hot with rice/pulao.
Notes
I used ghee for this. I cooked potatoes on stove top, not in a pressure cooker.