Burnt-Sugar Chiffon Cake

In a small heavy skillet, heat sugar until golden brown. Gradually add water; cook and stir until sugar is dissolved. Set aside. Let egg whites stand at room temperature for 30 minutes.
Position oven rack to lowest position. Preheat oven to 325u0b0.
In a large bowl, combine flour, sugar, baking powder and salt. In another bowl, whisk egg yolks, oil, water, vanilla and 6 tablespoons reserved syrup. Add to dry ingredients; beat until well blended. In another bowl, beat egg whites and cream of tartar until stiff peaks form; fold into batter.
Gently spoon into an ungreased 10-in. tube pan. Cut through batter with a knife to remove air pockets. Bake on the lowest oven rack 45-50 minutes or until cake springs back when lightly touched. Immediately invert pan; cool completely, about 1 hour.
Run a knife around side and center tube of pan. Remove cake to a serving plate.
For frosting, in a small saucepan, melt 2 tablespoons butter. Stir in flour and salt until smooth; gradually add remaining syrup mixture. Bring to a boil; cook and stir 1 minute or until thickened. Transfer to a small bowl; beat in the confectioners' sugar, milk and vanilla. Cool to room temperature.
In a large bowl, beat remaining butter until fluffy, about 5 minutes. Gradually beat in confectioners' sugar mixture. Spread frosting over top and sides of cake.