Sift the flour with the baking powder, beat the butter/margarine with a mixer for 5-6 min, add the sugar and continue beating another 2-3 min.
Add the lightly beaten eggs to the mixture, plus the grated rinds of the oranges, the vanilla, salt. Mix the juice from the oranges with the baking soda and add it to the mixture.
Knead a little until it's no longer sticky - the dough needs to remain soft. Leave it to rest for 30 min., covered. Make cookies of various shapes.
You can smear them with egg or milk on top. Bake in a preheated oven for 25-30 min. until reddened.