Boil your spaghetti in well salted water.

In a frying pan over low heat, melt the butter, anchovies, and chili.

Let the anchovies melt gently into the butter. (The butter can foam a little but not go brown.) Add the garlic clove.

Add 1 ladle of starchy pasta water. Toss or swirl until cloudy and creamy. Remove garlic. This is your emulsified base.

Add the lemon zest and a squeeze of lemon juice. Keep the heat gentle so the sauce stays glossy.

Transfer the cooked spaghetti straight to the pan. Toss to coat, adding splashes of pasta water until the sauce clings beautifully. The more you toss or twirl, the better the result.

Taste and adjust with lemon, pepper, and a little pasta water if it thickens. You shouldn’t need salt but taste to be sure.

Turn off the heat and fold through the chopped parsley.

Serve with extra zest, pepper, and a little more parsley on top.