In a large pot, bring salted water to a boil. Add the spaghetti and cook according to package instructions until al dente. Reserve 1/2 cup of the pasta water, then drain the pasta and set aside.
In a food processor, combine the avocados, minced garlic, lemon juice, basil, and Parmesan cheese. Blend until smooth and creamy. If the mixture is too thick, add a little reserved pasta water to reach your desired consistency.
In a large mixing bowl, combine the drained pasta and the creamy avocado sauce. Toss until the pasta is evenly coated. If it appears too dry, gradually mix in more of the reserved pasta water.
Season with salt and pepper to taste. Adjust the lemon juice or add more herbs if desired for extra flavor.
Plate the creamy avocado pasta and garnish with halved cherry tomatoes and a sprinkle of crushed red pepper flakes for a kick, if you like.
Notes
For a vegan option, substitute Parmesan cheese with nutritional yeast.