Preheat oven to 350°F. For the Cake, mix flour and baking powder in medium bowl. Set aside. Beat eggs in large bowl with electric mixer on medium speed until very light and fluffy. Add sugar, Vanilla, Butter & Nut Flavor and salt; beat until well mixed. Stir in sour cream.
Heat milk and butter in medium saucepan until scalding. Gradually add milk mixture to egg mixture, beating on low speed. Add dry ingredients; beat well just until mixed. Stir in sprinkles. Pour into 13x9-inch pan sprayed with no stick cooking spray.
Line pan with foil with ends of foil extending over sides of pan. Use foil handles to remove cake from pan before frosting.
Bake 35 to 45 minutes or until toothpick inserted into center comes out clean. Remove from oven. Cool in pan 10 minutes. Remove from pan; cool completely on wire rack.
For the Frosting, beat butter and Vanilla, Butter & Nut Flavor in large bowl until light and fluffy. Gradually add confectioners' sugar, beating well after each addition and scraping sides and bottom of bowl frequently. Add milk; beat until light and fluffy. Stir in sprinkles. Frost top of cake before serving.