To make the beet-cashew sauce, pre-heat oven to 450ºF. Wrap beets in foil and place in a dish or on a baking tray. Roast for about 30 to 40 minutes, until the beets can be easily pierced with a sharp knife. Remove from oven, carefully unwrap, and set aside until cool enough to handle.

While the beets are roasting, make the pesto. Place garlic, pistachios, and nutritional yeast in the food processor. Pulse until finely chopped. Add beet greens, olive oil, lemon juice, and salt. Pulse until everything is finely blended, leaving a bit of texture and color. Transfer pesto to a small bowl and wash the bowl of the food processor.

While the beets are cooling, set a large pot of well-salted water on the stove to boil (water should taste like seawater). Cook pasta according to package directions. When done, reserve 1/2 cup of cooking water and drain the rest.

Peel the cooled beets with a sharp knife and cut into pieces. Place beets in the bowl food processor fitted with the s-blade. Add the cashews and reserved cooking water. Blend until smooth and creamy.

Transfer pasta to a large serving bowl. Add beet-cashew purée and toss until all the pasta is coated. Serve topped with pistachio pesto.