Preheat oven to 325 degrees.
Zest and juice oranges and set aside. In a mixing bowl add dry ingredients: flour, sugar, baking powder, and salt; mix well. In a separate bowl add wet ingredients: oil, egg yolks, juice and water, vanilla. Add the wet ingredients to the dry ingredients and mix until it looks like cake batter. In a third bowl add egg whites and cream of tartar, beat on high for 4 minutes, until stiff peaks form. Gently add the egg white mixture to the bowl of batter. Pour batter into a greased angel food cake pan or chiffon pan ( do NOT use a bundt cake pan, trust me!). Take center rack out of oven and position the other oven rack two up from the bottom. Bake at 325 degrees for 55 minutes. Let cake cool for 10-15 minutes. Use a knife to loosen the cake from the edges of the pan and carefully turn out onto a tea cloth. Let cake cool completely. Ice cake and enjoy.