In a deep pan, heat 2 cups of water to boiling. Add the grated bottle gourd to this boiling water and stir.
Cook for 1 minute and strain. Allow the bottle gourd to cool. When cool, press down in the colander to squeeze out all excess liquid.
Put the yogurt, sugar, red chili powder, salt to taste and chopped coriander in a mixing bowl and blend till smooth.
Add the cooled bottle gourd, cumin powder and stir to blend.Chill in the refrigerator and serve.