Preheat oven to 350 degrees F. Grease and flour two 9-inch cake pans.
In a medium bowl, sift together flour, cream of tartar, and baking powder; set aside.
In a large bowl, beat beat egg yolks until very thick and creamy. Gradually add sugar, a few tablespoons at a time, and continue beating until mixture is smooth and pale yellow. Stir in lemon zest and lemon juice; gently fold in the flour mixture until well incorporated.
In a large bowl of your electric mixer, beat egg whites until stiff peaks form. Fold 1/3 of the beaten egg whites into the egg yolk batter, then fold in remaining egg whites until no streaks remain.
Spoon batter into prepare cake pans. Bake approximately 20 to 25 minutes or until cake begins to pull away from sides of the pan. Remove from oven and let cool 10 minutes in the pan. Loosen edges with a knife and turn out onto wire cooling racks to finish cooling.
Prepare the Lemon Filling and Lemon-Orange Frosting.
When cake is completely cool, with a long-blade serrated knife, cut each layer horizontally in half to make four (4) layers.
Spread Lemon Filling between layers of the cooled cake. To keep cake from sliding to one side, insert a long wooden skewer into the middle and all the way to the bottom. Spread Lemon-Orange Frosting on sides and top of the cake.
Store cake in the refrigerator until serving time.
Makes 8 to 10 serving.
In a medium saucepan over medium-high heat, combine lemon zest, lemon juice, and sugar. Bring just to a boil; reduce heat to medium-low and simmer 5 minutes. Add butter and stir until it has melted. Remove from heat and let mixture cool to room temperature.
When cool, beat eggs into the lemon-sugar mixture until well blended. Return to heat and cook, stirring constantly, 10 to 15 minutes or until mixture thickens and coats a spoon. Remove from heat.
Cool in refrigerator until ready to use.
In a medium bowl, beat butter until it has the appearance of thick cream. Beat in the lemon zest, orange zest, and lemon juice. Stir in the powdered sugar and orange juice, a little at a time; continue beating until mixture is very smooth (stir in enough orange juice to make a spreadable frosting).
Robert E. Lee Cake Recipe: https://whatscookingamerica.net/History/Cakes/RobertLeeCake.htm