Finely zest the lemon, then squeeze it to collect the juice.

Bring a large pot of water to a boil, then season it lightly with salt.

Cook the spaghetti in the boiling water until very al dente, about 2 minutes less than the package directions.

Reserve about 240 ml (1 cup) of pasta cooking water, then drain the spaghetti.

Melt the butter gently in a large frying pan over low heat, then add the anchovies.

Stir the anchovies into the melted butter until they dissolve into a smooth sauce, without browning the butter.

Add the drained spaghetti to the anchovy butter, then toss it over low heat.

Add reserved pasta water a little at a time, then toss until the sauce becomes glossy and creamy.

Remove the pan from the heat, then toss the pasta with lemon juice and lemon zest.

Divide the pasta among 4 plates, then grate mullet bottarga over each serving.

Finish with black pepper and taste before adding a small amount of salt if needed.