Agra ka Petha

Cut winter melon (Ash gourd) into half, remove skin and seeds and cut into pieces of desired size. Prick them with a fork or any other pointed thing. 
Place melon pieces in a large pan and pour sufficient water to deep the pieces into it. Add alum powder and boil for about fifteen minutes. Take out the pieces, drain and wash thoroughly under running water. Add sugar with one cup of water and heat till sugar dissolves. Add lemon juice to remove scum. Reduce heat to medium and add boiled melon pieces. Continue cooking till melon get softened and sugar syrup is of three-thread consistency. Switch off the gas, remove melon pieces and keep separately, so that they do not stick to each other. Serve when cool. 
The resultant sweet is called "Petha". This is famous sweet from Agra, India. You must taste it whenever you visit the Agra.