Ingredients:
1 lemon
12 oz. spaghetti or other long pasta
Kosher salt
¾ cup heavy cream
6 Tbsp. unsalted butter
¾ cup finely grated Parmesan
Freshly ground black pepper

Total cooking time:
45 mins

Recipe:

1. Using a lemon zester, zest a lemon and capture over a small bowl, separated into two piles.
2. Cut lemon in half and squeeze out enough juice to yield 2 Tbsp. into a small bowl; set aside.
3. Cook pasta in another large pot of boiling heavily salted water, stirring occasionally (olive oil not needed)
4. ​While pasta is cooking, add heavy cream to pot with one pile of the lemon zest and cook over medium heat, whisking often, until liquid is just beginning to simmer.
5. Reduce heat to medium-low, and slowly whisk in butter until melted and sauce is creamy and emulsified. Remove from heat.
6. Just before pasta is finished cooking, scoop out 1½ cups of warm pasta water and add half of that to the cream sauce and return to medium heat.
7. Using tongs if available, transfer spaghetti to pot with sauce.
8. Cook, tossing often and adding Parmesan little by little, until cheese is melted and sauce is creamy. You can add additional pasta water to loosen. 
9. Stir in reserved lemon juice; season with more salt, if needed.
10. Divide pasta among bowls. Season with pepper, then top with reserved lemon zest.