In a 3cup saucepan, combine the water and 2/3 cup sugar. Place over low heat to dissolve the sugar, then increase the heat to medium high and boil, without stirring, until a candy thermometer reads 235 degrees. (Wash down any sugar crystals slinging to the sides of the pan with a brush dipped in cold water.) Near the end of the boiling time, whip the egg whites with the cream of tartaruntil soft peaks form. Add the 2 tablespoons sugar, and continue to whip until the whites are stiff butnot dry. With the mixer running, pour the syrup onto the whipped whites. Continue to whip onmedium speed, about 3 minutes more. Mixture will thicken, cool and form glossy, stiff peaks. Addthe vanilla. Cool to room temperature, about 8 to 10 minutes, then frost cake right away.