For the Cake
Preheat oven to 350 degrees F.
Coat bottoms of 2-9 inch round cake pans with wax paper. Coat wax paper with cooking spray. Dust with flour; set aside.
In a large bowl, beat sugar and 1/2 cup butter at medium speed until well-blended (5 minutes). Add eggs and egg white one, at a time, beating well after each addition.
In a medium bowl, combine flour, baking powder, and salt. Combine flour mixture to creamed mixture alternatively with milk, beginning and ending with flour mixture. Stir in vanilla extract.
Pour batter into prepared cake pans. Bake at 350 degrees for 30 minutes. Let cool in pans 10 minutes on a wire rack. Loosen cake layers from sides of pans using narrow metal spatula; turn out onto wire racks. Peel off wax paper; let cool completely.
For the Frosting
In a medium saucepan, combine brown sugar, evaporated skim milk, butter, corn syrup, and salt. Bring to a boil over medium high heat, stirring constantly. Reduce heat, simmer until thick (5 minutes), stirring occasionally. Remove from heat. Add powdered sugar and vanilla. Beat at medium speed until smooth and slightly warm. Cool 5 minutes (frosting will be thin, but will thicken as it warms).
Place one cake layer on plate. Spread with 1/2 cup frosting; top with another cake layer. Frost top and sides of cake. Store cake loosely covered in refrigerator.