Avocado Pesto Fettuccine

In a large pot of boiling salted water, cook the pasta according to package instructions. Meanwhile, in a small dry skillet, toast pine nuts over low heat until golden brown. Shake pan to brown evenly, about 5 minutes. Cut avocados in half and remove pits. Scoop out avocado with a spoon and add to the bowl of a food processor. Add pesto and lemon juice and pulse until avocado is incorporated and smooth. Transfer avocado pesto into a large mixing bowl. Add the pasta and half the cheese; toss together and transfer to a platter. Garnish with toasted pine nuts, remaining cheese, basil, and chili flakes. Drizzle with olive oil and serve immediately.