1. Sift cake flour, sugar, baking powder, and salt into a bowl.
2. Stir in the brown sugar.
3. Make a well; add oil, egg yolks, water, maple flavoring in order given.
4. Beat until smooth.
5. In another bowl beat egg whites and cream of tarter until very stiff (I would do this first).
6. Pour yolk mixture over whites, folding very carefully to prevent breaking whites.
7. Add walnuts.
8. Pour into an ungreased tube pan.
9. Bake 55 minutes in a 325 degree Fahrenheit oven; then for last 10 minutes at 350 degrees Fahrenheit; invert when done.
10. FROSTING:.
11. Melt butter until golden brown; don't scorch.
12. Remove from heat.
13. Stir in powdered sugar.
14. Blend in sweet cream and maple flavoring.
15. Beat until smooth.
16. Spread on chiffon or angel cake.