Sift the flour in a bowl, pour in the baking powder.
In another bowl mix the water and oil and pour them into the flour. Stir and knead a soft dough.
Roll out the dough into a thin sheet, cut out circles from it using a glass. Put a little rosehip marmalade in the middle of each, fold into a crescent and press on the edges with a fork.
Arrange the crescents in a buttered tray and bake about 15 min. - they will remain white, so don't bake too long.
Once the treats have baked, while still hot, roll them well in powdered sugar and arrange in a serving plate.