Heat the oven to 180°C/350°F, or 160°C/320°F fan. Grease and line an 8-inch/20-cm round cake tin or a 2-pound/900-g loaf pan with parchment paper.

Beat the softened butter, 175 g caster sugar, and finely grated lemon zest until pale, light, and fluffy. This usually takes a few minutes and creates the airy base that gives the finished cake its tender texture.

Beat in the eggs one at a time, mixing well after each addition. If the batter begins to look curdled, add a spoonful of the flour before adding the next egg.

Fold in the self-rising flour just until no dry streaks remain. If using all-purpose flour, combine it with 2 teaspoons baking powder and a small pinch of salt before folding it into the batter, and do not overmix.

Transfer the batter to the prepared pan and gently level the surface with a spatula. Bake for 35–40 minutes, until golden and a skewer inserted in the center comes out clean.

While the cake bakes, stir together the juice of 1 large lemon and the remaining 100 g caster sugar. Leave the sugar slightly grainy rather than dissolving it completely, because those crystals form the classic crunchy topping.

As soon as the cake comes from the oven, pierce it all over with a skewer or toothpick. Spoon the lemon-sugar mixture slowly over the hot surface so the juice sinks into the crumb while the sugar remains lightly crisp on top.

Let the cake cool completely in the pan before removing it. Slice with a sharp knife and serve plain, with tea or coffee, or alongside a spoonful of softly whipped cream.