Scrape the outer skin of the bitter gourd with a back of the knife or a spoon. Slit vertically to create a opening. Do not half. Spread it a little and scrape the inside clean. Remove the seeds and white part. Handle it gently so that it does not break into two. 

Then rub salt on the inside and outside of the bitter gourd. Leave it aside for 20 minutes. Then wash them well in cold water. Squeeze the excess water out and pat them dry gently. 

Heat oil in a pan over medium high. Once it is hot, add the onions and little salt. Let it sweat and the onions turn golden brown. 

Once it softens, add besan and all the spice powders. Keep stirring until the onions brown nicely. Then add grated raw mango. Let it cool.

Now, carefully stuff the filling inside each bitter gourd and tie them with a string, so that it does not fall apart. 

Heat oil in a cast pan Place the stuffed bitter gourd carefully in a single layer. Keep turning and cook them until they brown on all sides. Keep the flame low to medium. 

Remove and drain the excess oil. Serve them with roti or phulkas.