Begin by bringing a large pot of salted water to a rolling boil over high heat. Add your fettuccine or spaghetti and cook according to the package instructions, typically around 8-10 minutes, until al dente. Once cooked, drain the pasta in a colander, making sure to reserve ½ cup of the pasta water for later use.

In a high-powered blender, combine the ripe avocados, roasted red peppers, garlic, fresh basil leaves, lemon juice, olive oil (if using), and salt. Pour in half of the reserved pasta water, then blend the mixture on high until it becomes creamy and smooth, which should take about 1-2 minutes.

After blending your sauce, check its thickness. If it's too thick for your liking, gradually add more of the reserved pasta water, a tablespoon at a time, blending after each addition.

In a large mixing bowl, toss the drained pasta with your creamy avocado bell pepper sauce, ensuring every strand is well-coated. Serve your vibrant dish warm, garnished with lemon zest and additional fresh basil.