3 cups all purpose flour
1/2 tsp baking powder
1/2 tsp baking soda
1/2 tsp salt
1 cup buttermilk
2 tsp vanilla extract
3 sticks unsalted butter, at room temperature
1 lb light brown sugar
5 large eggs, separated, at room temperature
1/2 cup sugar
1 cup convectioners sugar
2 tbs milk
1/4 tsp vanilla extract
1. Preheat oven to 350'. Butter and flour a 10 inch tube pan or bundt pan.
2. Make cake: Mix dry ingredients in a bowl. Whisk buttermilk and vanilla in a small bowl. Using an electric mixer on medium-high speed, beat butter and brown sugar until fluffy. Beat in egg yolks, 1 at a time. Reduce speed to low; alternately add flour mixture and buttermilk, starting and ending with flour.
3. In a dry bowl, beat egg whites on medium-high speed until soft peaks form. Add sugar 1 tbsp at a time, beating until whites form stiff peaks. Fold 1/3 of egg whites into batter, then fold in remaining whites. Transfer batter to pan.
4. Bake 75-85 minutes, until a toothpick inserted in center comes out clean. Let cake stand in pan 10 mintues, invert onto wire rack; let cool.
5. Make glaze: Mix sugar, milk and vanilla in a bowl until smooth. Spoon glaze atop cake.