Prepare cake mix as directed on box. Prepare Fillables pan by spraying a light coat of baking spray. Pour batter into Fillables pan, filling about 2/3 to 3/4 full. Tap pan on counter to release air bubbles.

Bake according to cake package directions according to pan size. My pan was a 9" pan so I followed the instruction for baking a 9" pan. Cool in pan on wire rack for 10 minutes. Remove from pan to cooling rack to cool completely.

Place bottom on Fillables cake on serving plate, well side up. Fill wells with Key lime cream cheese filling. Spread remaining filling around cake as if you are icing it. Place top layer and sprinkle with confectioners' sugar.

While cake bakes prepare Key lime cream cheese filling. Refrigerate for a minimum of 30 minutes.

To make Key Lime cream cheese filling:
In a large bowl, beat the cream cheese, milk and juice until smooth; fold in whipped cream.