Cook the pasta. Bring a large pot of salted water to a boil. Add the pasta and cook until al dente, 8 to 10 minutes, or according to package directions. Meanwhile, make the sauce.
Make the sauce. Scoop the avocado flesh into a blender. Add the basil, spinach, garlic, lemon juice, and salt. Blend until smooth, about 1 minute. With the blender running, drizzle in the olive oil and blend until incorporated; set aside.
Drain the pasta. Drain the pasta in a colander, then transfer to a large bowl.
Toss the pasta with the sauce. Pour the sauce from the blender onto the pasta and toss to coat. Serve immediately.
