Bright grated lemon.
A silky butter-Parmesan coating.

Next: ingredients
for four servings.

1 medium unwaxed lemon (freeze whole; use about 1/3)
12 oz dry spaghetti
2 tsp kosher salt, for the pasta water
3 tbsp unsalted butter
3/4 cup finely grated Parmesan
1/4 tsp freshly ground black pepper
3/4 cup reserved starchy pasta water

Small freezer-safe tray or bag
Large pot
Fine grater or microplane
Large heatproof mixing bowl
Tongs · liquid measuring cup
Measuring spoons

Scrub and thoroughly dry the unwaxed lemon, then freeze it whole until solid, at least 8 hours.

Visit the recipe for all instructions.