For the cake: Preheat your oven to 350F and grease two, 9 inch round pans. Set aside. Using a stand mixer or hand mixer, cream the butter, sugar, salt, and vanilla until light and fluffy (about 5-10 minutes).
Incorporate the eggs one at a time. In a medium bowl, whisk together the flour and baking powder and in a smaller bowl whisk together the milk, orange juice, and white vinegar.
Add the dry ingredients and the wet ingredients, alternating each until everything is mixed in. Do not over mix!
Pour batter into greased pans and bake for 45 minutes, until golden brown. Let cakes cool all the way through before filling and decorating.