Courtesy of Cook's Illustrated.

Serves 2

1/2 lb spaghetti
Olive Oil
1 small shallot, minced (about 1.5 Tbsp)
1/8 cup heavy cream
1/8 cup lemon juice
1 tsp finely grated lemon zest
1/4 cup finely grated Parmesan cheese, plus more for serving
1 Tbsp shredded fresh basil leaves
Salt and pepper

Bring 2 quarts of water to boil in a saucier pan.
Add 1/2 Tbsp salt and pasta to boiling water.
Cook, stirring frequently, until al dente.
Reserving 1 cup cooking water, drain pasta into a colander and set aside

Heat 1 Tbsp oil in now-empty pan over medium heat until shimmering.
Add shallot and 1/2 tsp salt; cook until shallot is softened, about 2 minutes.
Whisk 3/4 cup of reserved pasta water and cream into pot.
Bring to simmer and cook for 2 minutes.

Remove pot from heat, return pasta, and stir until coated.
Stir in 1.5 Tbsp olive oil, lemon zest, lemon juice, parmesan, and 1/4 tsp pepper.
Cover and let stand for 5 minutes, tossing frequently; sauce will thicken slightly as it cools.
Stir in basil leaves and serve.