Instructions: 

1. Using a vegetable peeler, remove two 2 (2-inch) strips of zest from the lemon. Thinly slice each strip lengthwise into thin strands. Set aside. Finely grate remaining lemon zest into a large Dutch oven. 
2. In a small bowl, cut zested lemon in half and squeeze out enough fresh lemon juice to yield 2 Tbsp. Set aside.
3. Cook pasta in a large pot of boiling water, stirring occasionally, until very al dente, about 10-12 minutes (pasta will finish cooking in the sauce). Drain and set aside.
4. Meanwhile, add heavy cream to Dutch oven with lemon zest and cook over medium heat, whisking often, until liquid is just beginning to simmer, about 2 minutes. Reduce heat to medium-low. Whisk in butter, 1 Tbsp. at a time, until melted and sauce is creamy and emulsified. Remove from heat.
5. Just before pasta is al dente, scoop out 1-½ cups pasta water. Add 3/4 cup pasta water to cream sauce and return to medium heat. Using tongs, transfer pasta. Cook pasta, tossing often, and adding Parmesan cheese, little at a time, until cheese is melted and sauce is creamy, about 3 minutes. Remove from heat and stir in reserved lemon juice. Add 1 Tbsp. pasta water at a time if sauce looks too thick. Season with salt & pepper, to taste.
6. Divide pasta into serving dishes and garnish with Parmesan. Serve and enjoy!