Heat oven to 375 degrees. Grease and flour a jelly roll pan, or grease and line it with parchment paper or aluminum foil. Measure flour by dip and level method. Blend flour with baking powder and salt. In a mixer bowl, beat the egg until very thick and lemon colored and gradually add sugar. Blend in the water and vanilla on low speed. Slowly mix in the dry ingredients at low speed just until a smooth batter results. Pour into the pan and bake 12-15 minutes. Loosen edges and turn out onto a towel, saran wrap, or aluminum foil lightly sprinkled with powered sugar. Cool the cake and cut into pieces for the torte. (I usually use 4 or 5 pieces).