
In the time it takes to bring a large pot of water to a boil, you can make a batch of herby, bright and spicy green chutney, also known as hari chutney (hari means “green” in Hindi). When combined with Parmesan, butter and pasta water, the chutney transforms into a silky, tangy sauce that clings perfectly to pasta. This chutney is a classic South Asian cilantro-based version, but feel free to incorporate other tender herbs like dill, mint or basil.
Bring a large pot of salted water to a boil over high heat.
Meanwhile, add cilantro, chile, garlic, lemon juice and 1 teaspoon salt to a blender or small food processor. Blitz until smooth, adding water by the tablespoonful as needed to help the blending. (You should have between ¾ cup to 1 cup of chutney.)
Add spaghetti to the boiling water, toss with tongs, and cook until nearly al dente, 8 to 9 minutes. Just before draining, reserve 1 cup pasta water. Drain pasta and transfer it back to the pot.
Over low heat, add the butter, Parmesan, green chutney and ¼ cup pasta water to the pasta and toss vigorously until everything is combined and the sauce clings to the noodles, adding more pasta water as needed to form a silky sauce.
Taste for salt, adjusting to preference, and serve immediately with more Parmesan.