Bring a large covered pot of salted water to boil.
Prep the beets: Wash, cut off the tops and roots, then peel the beets with a vegetable peeler. On a cutting board, cut each beet in half, then into slices, then into cubes. Set aside.
Make the sauce: In a large enough skillet to hold the pasta, sauté the garlic and chili pepper in olive oil for about 2 minutes over medium heat. The garlic should not, or just barely, start to color. Add the beets immediately along with ½ cup of water, cover and cook until tender, about 10 to 12 minutes (adding a little more water, if necessary, to keep them from drying out).
Meanwhile, cook the pasta: Add the pasta to the boiling water and cook, stirring occasionally, untilal dente, tender yet still firm to the bite.
Toss: Using a pasta fork or tongs, transfer the pasta straight from the water to the skillet of beets, along with ½ cup of the starchy cooking water, and toss over medium-high heat until the deep ruby sauce is evenly distributed throughout the pasta. Sprinkle with fresh parsley, if using, and serve immediately.
Notes
If your beets have stalks, you can add them too, in bite-sized pieces or smaller. They add a subtle yet nice flavor dimension similar to Swiss chard, plus more nutrients and beautiful color. Or save them with the extra nutritious bitter greens to sauté up with garlic as a side for another meal.