Preheat oven to 325°F. Invert the bottom of an 8-inch springform pan (to make it easier to slide the cake off the bottom) then lock on the sides of the pan. Lightly grease and flour the bottom and sides of the pan. Line the bottom of the pan with parchment paper.
In a small bowl combine the flour, salt, baking powder and baking soda. Set aside.
In a large mixing bowl combine the butter, lemon and orange zests and sugar. Beat on medium for several minutes until the mixture is light and fluffy. Scrape down the sides of the bowl as needed.
Add the eggs, one at a time and blend just until the yolk disappears. Scrape the sides and bottom of the bowl and blend again.
In a measuring cup with a spout, combine the vanilla, sour cream, lemon juice and orange juice and stir to combine (the mixtures may seem curdled). Add ⅓ of the flour mixture to the creamed butter and sugar. Beat on low until incorporated. Add ⅓ of the juice mixture and blend until smooth. Do not over beat. Repeat adding ½ of the remaining flour, then ½ of the remaining juice until both are incorporated. Add the last of the flour and juice and blend once more. Scrape the bottom and sides of the bowl and gently stir with a spatula once more.
Pour the batter into the prepared pan and spread evenly. Bake in preheated oven for 50-60 minutes or until the top is lightly browned and a toothpick inserted in the center comes out almost clean. A few moist crumbs is okay - but no wet batter.
Cool the cake on a wire rack for at least 30 minutes before removing the sides. Cool completely before glazing.