Step 1
In a large heated saucepan, heat olive oil. Add lemon zest and garlic. Sauté over medium-low heat until fragrant, about 3 minutes.
Step 2
Cook pasta in a large pot of boiling heavily salted water (not a pinch of salt; handsful). Stop cooking pasta just before al dente. The pasta will finish cooking in the sauce. Scoop out 500 ml (2 cups) of pasta water just before the pasta is done and set aside.
Step 3
Meanwhile, add cream to saucepan with lemon zest and garlic. Cook over medium heat, stirring often, until cream is simmering. Reduce heat to low and stir in 15 ml butter at a time until sauce is emulsified. Remove from heat.
Step 4
Add 125 ml (½ cup) of pasta water to cream sauce and return to medium-low heat. Transfer spaghetti to saucepan with sauce. Continue cooking pasta in sauce while adding the parmesan little by little until sauce is creamy and cheese well incorporated, about 3 to 4 minutes. Stir in lemon juice and season with ground black pepper and salt to taste. Taste again and add more lemon juice if you prefer it to be more acidic.
Cream sauces tend to thicken quite quickly as they cool. Add more pasta water (2 tablespoons at a time) to make it more saucier if you prefer saucy pasta.
Serve with more parmesan and black pepper.
