In a medium pot, combine sugar, water, salt and cream of tarter. Cover mixture and let boil 5 minutes.
Uncover the pot after the 5 minutes of boiling have elapsed, wipe the sides of the pot with a damp cloth. Continue boiling until the mixture reaches the firm ball stage.
Pour the mixture over stiffly beaten egg whites, and stir in vanilla. Continue beating until the candy holds its shape when dropped from a spoon. Drop the mixture by spoonfuls onto wax paper, let cool.