• 315 g(11 oz/2½ cups) plain (all-purpose) flour
• 3 teaspoons baking powder
• 90 g(3¼ oz) caster (superfine) sugar
• freshly ground nutmeg
• 2 eggs
• 250 ml(9 fl oz/1 cup) buttermilk
• 60 g(2¼ oz) butter, melted
• 1 teaspoon grated lemon zest
• 150 g(5½ oz) fresh blueberries
• 2 tablespoons demerara sugar

Preheat the oven to 200°C (400°F/Gas 6). Grease and flour a 30 × 20 cm(12 × 8 inch) tin with sides at least 5 cm(2 inches) high. Sift the flour and baking powder into a large bowl and add the sugar and a few good grinds of nutmeg. Put the eggs in a bowl and whisk until light and fluffy. Add the buttermilk, butter and lemon zest and beat together well. Pour into the dry ingredients and mix gently with a wooden spoon just until everything is combined. If you beat too hard the cake will be tough.

Spoon the mixture into the tin, spreading it thinly to reach all four sides. Scatter the blueberries over the top and sprinkle these with demerara sugar. Put in the oven and bake for about 25 minutes, or until a skewer poked into the centre of the cake comes out clean. Leave to cool in the tin before cutting into squares. This keeps well in a biscuit tin for up to a week.