Place dries (flour, baking powder, baking soda, salt) in a bowl, stir well, and set aside. In a large bowl, beat egg whites on high speed of an electric beater until stiff peaks form; set aside.

Combine water and fresh-squeezed orange juice in a separate bowl. Set aside.

In a large bowl, cream butter and sugar together until light and fluffy. Add orange zest and mix well. Alternately add flour mixture and juice mixture, beginning and ending with dries.

Gently fold in beaten egg whites and spread into two, well-greased or parchment-lined 8-inch cake pans. Bake at 350 degrees for approximately 25 minutes, or until center springs back when touched. Cool completely, and cut each layer in half horizontally. Can make a day ahead and refrigerate.

Mix eggs and sugar well. Add orange juice, orange zest, and salt. Heat over medium-high heat, stirring constantly, until mixture thickens. Remove from heat and stir in butter. Cool before spreading over half-layers of cake.

In a large bowl, cream butter with salt and half of the powdered sugar. Add orange juice a little at a time, adding remaining sugar to get to desired spreading consistency. Spread between whole layers and on top of the cake. If you’re good at it, and you have enough frosting, spread remaining frosting on sides of the cake! (I’m not that good, so I often just frost in between layers and on top!)