Preheat your oven to 350°F. In a large mixing bowl, combine the yellow cake mix, milk, eggs, and oil, then beat on medium speed for two minutes until smooth. Gently fold in the lime zest and raspberries. Transfer the batter into a 13 x 9-inch baking dish and bake for 30 to 40 minutes, or until a toothpick inserted in the center comes out clean.

In a separate bowl, combine the sweetened condensed milk, key lime juice, heavy cream, and lime zest. Stir until well mixed; the texture will be thick. Set aside.

For the topping, whip the heavy cream until it holds stiff peaks. Blend in the powdered sugar, then transfer the whipped cream to another bowl. In the same mixing bowl, beat the cream cheese until smooth. Gradually incorporate the whipped cream into the cream cheese mixture and blend until fully combined. Chill this topping mixture until it's ready for use.

Once the cake has baked and slightly cooled, use the handle of a wooden spoon to poke multiple holes throughout the cake. The more, the better. Carefully pour the prepared filling over the warm cake, using a spatula to guide it into the holes. It's fine if some of the mixture remains on the surface. Cover and refrigerate the cake overnight.

The following day, spread the whipped topping evenly across the cake’s surface. Garnish generously with lime slices, additional zest, and raspberries before serving.