Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch baking pan.
In a large bowl, combine the cake mix, eggs, oil, lemon zest, lemon juice, and water. Beat with an electric mixer on low speed for 2 minutes, or until all ingredients are combined. Pour into the prepared pan.
Bake for 25 minutes, or until a toothpick inserted into the center comes out clean. Let cool completely.
In a medium bowl, beat the cream cheese and condensed milk until smooth. Stir in the flour and salt until well blended.
Pour the cream cheese mixture over the cooled cake. Refrigerate for at least 4 hours.
In a medium bowl, beat the heavy cream and powdered sugar until stiff peaks form. Spread over the chilled cake.
Serve chilled.
Interesting Facts
Lemon Ice Box Cake is a classic American dessert that dates back to the late 19th century.
The name "ice box cake" comes from the fact that the cake was traditionally made in an ice box, which was a type of refrigerator.
This recipe was a favorite of First Lady Eleanor Roosevelt.