Baking on Friday: Orange Sunshine Cake with Orange Buttercream Frosting

Tomorrow is Mike's birthday.  He's really old!!  His grandmother used to make a birthday cake she called a "Sunshine Cake" and it was his favorite cake growing up.  I have her old recipe, but it's written in a way that doesn't make sense to me, using terms that I'm not familiar with.  I don't know how old the recipe is, but it was written using terms that are not in common usage today. 

I did a search one day for Sunshine Cakes and found all kinds of cakes that would fit the bill.  Most are made with yellow cake mix.  In fact, Mike's mother advised me just to make the cake that way and to add some orange to the frosting.  That suited for a while, but I found myself wanting something a little more elegant.  After reading many recipes, I came up with this composite of recipes and frostings.  Mike thought it tasted just like the one his grandmother used to make.  Here's what I came up with:

Orange Sunshine Cake with Orange Butter Cream Frosting

For cake:
8 eggs
1 1/2 cups sugar -- divided
1 cup plus 2 tablespoons cake flour
1 orange -- cut in half, juiced, zested, and divided
1 pinch salt
1 teaspoon cream of tartar

For Orange Butter Cream Frosting:
2 sticks unsalted butter -- at room temperature
2 1/2 cups powdered sugar
Orange juice from the 1/2 orange above

Preheat oven to 300 degrees.

Separate eggs. Beat yolks until thick, and to the yolks gradually add 1/2 cup sugar with the flour and continue beating. Add grated zest and juice of half of the orange.

Beat egg whites gently until foamy. Add pinch of salt and the cream of tartar. Increase the mixer speed and add 1 cup sugar gradually and beat egg whites stiff.

Pour the egg yolk mixture in a thin stream over the entire surface of the egg white mixture, gently cutting and folding with a rubber spatula, making sure everything is completely folded. Pour into an ungreased 10-inch round tube pan with a removable bottom. Draw a thin spatula gently through the batter to get rid of any large air pockets.

Bake 1/2 hour in 300 degree oven and 1/2 hour more in 325 degree oven. Invert until cooled.

For Frosting: Combine butter and sugar in a medium bowl. Add just enough orange juice from the remaining 1/2 orange to thin the frosting to a spreading consistency. Frost when cake is completely cooled. Garnish top of cake with orange zest.