Pour the lemon juice at the bottom of the blender first and then add the onion, ginger, garlic, serrano, and cumin. Blend for less than a minute or so, until it is chopped up a bit.
Add the cilantro and get blending until smooth. If your blender is having a hard time liquifying the chutney, try scraping down the sides between blending and gradually increasing speed. If you're still having trouble, add a tablespoon of water at a time until things start moving.
Add salt to taste, and enjoy! Eat with all your favorite savory Indian dishes, or even other things -- potatoes, pizza, tacos, toast, the choice is yours!