Preheat the oven to 350-degrees and grease a whoopie pie pan.
Sift together the flour, sugar, baking soda, and salt into a medium bowl and set aside.
In a large mixing bowl, whisk together the milk, eggs, softened butter, orange zest and vanilla. Slowly add the dry ingredients and mix until smooth.
Spoon the batter into the prepared pans. Do not fill the wells more than 2/3â??s full. Bake for 12-15 minutes until a tester comes out clean.
Remove from the pan from the oven and let set for 10 minutes before turning out onto a rack to cool completely.
Whisk together the sugar, orange extract and butter, adding the milk as needed. Beat for about 3 minutes until fluffy and thick.
Mix in enough of the orange food coloring to turn the frosting the desired color of orange, if desired.
Spoon the frosting into a piping bag and pipe onto one cake, place a second cake on top.