In the bowl of an electric mixer, fitted with the whisk attachment, beat butter (on medium speed) until completely smooth (30 seconds to a minute).
Add cream cheese, and then beat until smooth.
One cup at time, add 2 cups of powdered sugar, beating after each addition.
Add vanilla, and blend to combine.
Add about 2 tablespoon of cream, and continue beating.
Add the remaining 3 cups powdered sugar, one at a time.
Add an additional 1 tablespoons cream until desired consistency is reached.
Add salt.
Continue to beat another minute or so. The frosting should now be smooth and fluffy.
Scoop about 1 cup of frosting into a bowl and set aside. This will be the white frosting for the top portion of the cake.
Into another bowl, scoop about 2 1/2 cups of frosting and set aside. This will be colored orange later.
Remaining in the bowl should be about 1+ cup of frosting. Color this frosting yellow. Add this yellow frosting to a large piping bag, fitted with a large round tip.
Now, put the frosting that was reserved to turn orange back into the mixing bowl (no need to clean out) and color it orange. Add the orange frosting to a large piping bag fitted with a large round tip.