Mix the flour, yeast, caster sugar and 1 tsp sea salt in a large bowl. Make a well in the centre and pour in the warm milk, beaten egg and melted butter. Mix well a soft dough forms. If it feels dry, add a bit of warm water, if it feels too sticky and wet, add 1 tbsp flour.
Dust a work surface with flour and tip the mixture onto it. Knead the dough until it feels smooth and elastic. Shape into a ball and put in a large, lightly floured bowl. Cover and leave to rise in a warm place for 1 hr or until doubled in size. Or, leave to prove in the fridge overnight, removing 45 mins before continuing.
Line a large baking tray with non-stick baking paper. Lightly dust a work surface and roll out the dough to 30 x 45cm. Evenly spread the lemon curd over the dough and sprinkle with the sultanas. Roll the dough up lengthways from the shortest side, like a Swiss roll, to form a log. Cut into 12 equal sized buns with a sharp knife, egg-washing the loose end of the pastry and pressing it down, so it doesn’t unravel. Arrange, spread apart, on the prepared baking tray, cover, and leave to prove for 45 mins until doubled in size.
Heat the oven to 200C/180C fan/gas 6. Brush the buns with a little egg wash. Bake for 10 mins, then reduce the temperature to 180C/160C fan/gas 4 and cook for a further 10 mins. Leave to cool.
Meanwhile, sieve the icing sugar and mix with 3 tbsp water until a thick, white icing forms. Spread the icing on top of the buns with the back of a spoon, then put a cherry in the middle of each one.