Beat cream cheese, softened butter and lemon extract in a bowl until light and fluffy. Add in your yellow food coloring if using (3-4 drops is perfect for a light yellow shade). Mix until well combined.
Add in your confectioners sugar, one cup at a time, mixing well after each addition.
Add in three tablespoons milk, and mix until very well combined. If you desire a thinner frosting, add additional two tablespoons of milk, one at a time, mixing well after each addition. Once desired consistency is reached, fold in the zest of one lemon.
Once cake has cooled completely, apply frosting to cake. As this is a bundt cake, it does not have to be perfectly frosted. Garnish with remaining lemon zest.
Store in refrigerator.