Preheat the oven to 400°F/200°C.

In a large bowl, massage the sugar and lemon zest together with your fingers until the sugar turns fragrant and slightly fluffy.

Mix in the egg yolks, then the milk, then the flour. Set aside.

In a clean bowl, whip the egg whites until they reach stiff peaks.

Fold 1 heaping tablespoon of the egg whites into the batter to loosen it, then gently fold in the remaining egg whites in two batches, being careful not to deflate them.

Pour the batter into a loaf pan lined with parchment paper.

Bake for 10 minutes, then remove and cut a slit down the center of the cake.

Reduce the oven temperature to 350°F/180°C and continue baking for 30–35 minutes, or until a knife inserted in the center comes out clean — running the knife through that same slit once more around the 10-minute mark to help it rise evenly.

Let the cake cool at room temperature for 15 minutes, then wrap it in cling wrap and refrigerate overnight.

Whisk together the powdered sugar and lemon juice, adjusting the ratio to taste until you get a glaze you like.

Drizzle over the chilled cake before serving.