Bring 4 quarts salted water to a boil in a large pot. Add the pasta and boil until tender but firm.
Stir 2 tablespoons of the hot pasta water and the heavy cream into the pesto. Drain the pasta in a colander and return it to the hot pot. Stir in the pesto and toss well to combine.
Serve immediately on warm plates. More freshly ground pepper is welcome