Wash pavakka and trim both ends. Slice in half lengthwise and remove seeds and pith. Slice in half again and cut into small pieces.
Place in a bowl. Sprinkle with salt, turmeric and chili powder. Mix well, cover and set aside for at least 30 minutes.
Heat up three tablespoons vegetable oil in a heavy bottomed pan. When oil is very hot, add mustard seeds. When almost finished popping, add red chili, then curry leaves (removed from stem). Add onion and mix. Add bitter melon (including any accumulated juices). Stir, cover and cook on medium low heat until golden brown to brown (20 to 30 minutes). Stir every few minutes adding more oil if bitter melon is sticking to bottom of pan. Taste and adjust cooking time to your liking. Taste and add more salt if necessary.
Stir in a teaspoon or two of coconut oil, 1/4 tsp roasted cumin powder and 1/4 tsp amchur powder for sourness. These are all optional but enhance the taste of the dish.