Step 1

In a large skillet, melt butter over medium heat until foaming. Lower heat to low, add lemon zest and garlic, and cook, stirring, until fragrant, 1 to 2 minutes.

Step 2

Meanwhile, in a medium pot of boiling salted water, cook pasta until just shy of al dente. Reserve about 1 cup (240ml) of the starchy pasta water, then drain pasta.

Step 3

Add pasta to butter mixture, along with 1/2 cup (120ml) reserved pasta water. Increase heat to medium-high and cook, stirring and tossing to coat, until pasta is glazed in a satiny, emulsified sauce.

Step 4

Add grated cheese and toss and stir rapidly until sauce thickens; if it becomes too tight and dry at any time, add more pasta-cooking water to loosen it sufficiently. Add lemon juice to taste, starting with 1 tablespoon (15ml), then adding more until desired tartness is reached. Season with salt and pepper.

Step 5

Serve spaghetti right away, topping each serving with additional grated lemon zest and cheese.