Preheat oven to Gas 6, 200°C, fan180ºC and line a 12-hole muffin tray with paper cases.
Simmer the cranberries with 50g (2oz) of caster sugar for 6-8 minutes, shaking the pan regularly until you have a thick glaze.
Sift the flour and the baking powder into a large bowl and stir in 150g (6oz) caster sugar.
In another bowl, whisk together 2 large eggs, the melted butter the buttermilk. Fold this mixture into the flour and stir the cranberries through.
Spoon into paper cases and bake for 20-25 minutes until cooked and golden.