- Scrub the beet or beets and put in a large pot. Cover with water by 1 to 2 inches. 
- Boil until tender enough to slide a knife into the center with ease (about 45 minutes). If the water drops below the beet(s), add more and bring to a boil again. Once tender, drain and set aside until cool enough to handle. 
- Cook the pasta in a large pot of lightly salted boiling water until al dente. Scoop up 1 cup of pasta cooking water and set aside. Drain remaining water. 
- While the pasta cooks, remove the skin from the beets. Cut into quarters and put in a blender. 
- Add ΒΌ cup reserved pasta cooking water to the blender along with the ricotta, olive oil, lemon juice, and 1 teaspoon salt and run until smooth. 
- Transfer the pasta to a serving bowl or platter. Pour the sauce over the top and toss to coat well. 
- Sprinkle the walnuts or slivered almonds over the pasta. If desired, garnish with grated Parmesan cheese and basil. Serve immediately.