Preheat the oven to 350°F. Butter or spray with non-stick cooking spray 2 9-inch round pans.
In a large bowl, combine the cake mix, milk, eggs, oil and extract and beat with an electric mixer on low speed and increasing to medium speed for 1 minute.
Distribute the batter evenly into the prepared pans. Bake 24-26 minutes or until a toothpick inserted comes out clean. For successful cake removal, cool completely, run a knife along the edges of the pan , flip the pan over, and give the bottom of the pan a gentle pat to release onto a cooling rack.
For the icing, in a medium bowl, mix the sour cream, powdered sugar and extract with a whisk until well blended.
Fold in the Cool Whip.
Assemble the cake on a cake stand: cake layer one, 1/3 of the icing, cake layer 2, and the remaining icing on the top of the cake and all around the sides.
Refrigerate the frosted cake until ready to serve. For best results, refrigerate at least 2 hours prior to serving.