Heat butter in the pressure cooker along with the cinnamon stick. Add the onions, tomatoes and potatoes. Mix for a min or so then add the spinach and mix. Add salt, lots of pepper and a pinch of sugar. Add little water- cup and a half maybe (spinach gives out water) and close.
open after 3-4 whistles, let it cool, put it in a mixer (add more water if required). Add lime in the end. La la la!