Preheat oven to 190 (O/U). Grease baking sheet with light butter or butter.
Sift flour, baking soda and baking powder into a large baking bowl. Knead, adding enough buttermilk to make a soft dough.
Knead dough on a floured work surface until smooth. Place a 20 cm disc on the baking sheet, score deeply in a criss-cross pattern with a floured kitchen knife.
Brush with water and dust with a tiny bit of flour. Bake for 20 -half hours until the bread sounds hollow when tapped.