• Prepare and bake the 1 (14.25-ounce) box white cake mix, according to the package directions for a 9x13-inch pan. Remove from oven, let it cool for 5 minutes.
• Poke holes all over the cake using the handle of a slim wooden spoon, being careful not to poke all the way to the bottom, and set aside.

Filling:

• In a medium bowl whisk together the 1 (14-ounce) can sweetened condensed milk, ¾ cup whipping cream, 1 teaspoon lime zest, 4 drops yellow food coloring, 1 drop green food coloring, (if using). Last, stir in the ½ cup key lime juice, once you add the key lime juice, it will start to thicken pretty quickly.
• Pour the filling evenly over the top of the cake. Spread it back and forth so it fills the holes. Refrigerate for at least one hour or up to overnight.

Topping:

• Add the 1 ¼ cup whipping cream to a medium bowl that has been chilled in the freezer. Using a hand mixer, whisk the cream until frothy. Add the 1 teaspoon vanilla and gradually add the ¼ cup powdered sugar as you mix. whisk until peaks form.
• Spread the topping evenly over the cake and garnish with sliced strawberries, lime slices, and lime zest, if desired.