Add the spinach, parsley, cilantro, green onions, garlic, vegetable broth, olive oil, lime juice, salt, black pepper, and cumin to a blender. Blend until completely smooth and bright green.

Pour the green mixture into a medium saucepan and stir in the rinsed brown rice.

Bring to a gentle boil over medium-high heat, then reduce the heat to low, cover, and simmer for 35 to 40 minutes, or until the rice is tender and the liquid is absorbed.

Remove the pan from the heat and let it stand, covered, for 5 minutes.

Fluff the rice with a fork and taste for seasoning. Serve warm as a side dish or base for bowls.