In a large bowl, whisk together flour, baking powder, baking soda & salt. With fingertips, cut in cold butter until mixture resembles small peas. In a measuring cup, whisk together water, egg & vinegar. Make a well in dry mixture & pour wet mixture into it all at once. With hands, mix until JUST combined. Roll out pastry to about 1/8-1/4″ thickness Cut out 8 – 6-inch circles with a pastry cutter. Press into tart forms. Refrigerate for at least 30 minutes.