Rinse the quinoa in a fine-mesh sieve and set it aside.
Heat the oil in a large saucepan over medium-high heat.
Add the onion, cumin seeds, mustard seeds, ginger paste, garlic paste, turmeric powder, and red chili powder to the saucepan and cook for 3-4 minutes, until the spices are fragrant and the onion is softened.
Add the rinsed quinoa and the water to the saucepan and stir to combine everything evenly.
Bring the mixture to a boil, then reduce the heat to low and simmer for 15-20 minutes, until the water has been absorbed and the quinoa is cooked through.
Once the quinoa is cooked, add the lemon juice and stir to combine.
Season the quinoa with salt, to taste.
Serve the Indian-style lemon quinoa hot, topped with chopped cilantro if desired.