Preheat the oven to 200°C/gas mark 6. Mix all the ingredients for the doughnuts together in a large bowl to create a smooth batter.
Lightly grease a 6-hole doughnut tin with the melted butter. Fill the holes in the tin with batter to about one-third full and bake for about 12 minutes, until risen and slightly browned.
Remove from the oven and leave to cool while you cook the rest of the doughnuts. It should result in about 18–24 doughnuts, depending on how much batter you use.
To make the icing, mix the sugar with the rose water and lemon juice in a bowl until it is a thick white paste. Dip the doughnuts into the icing or drizzle it over the top to serve.