Preheat the oven to 350 degrees. Spray a 9×13 pan with nonstick spray.
Make and bake the lemon cake mix according to the package directions.
Let the cake cool for 5 minutes, then use the handle of a wooden spoon to poke holes all over the warm cake.
Pour the sweetened condensed milk over the top of the cake, letting it soak into the holes.
Remove the foil liner from the can of frosting. Microwave the frosting for 30 seconds. Stir and pour over the top of the cake. Spread it out with a spatula.
Let the cake cool for an hour, then refrigerate until completely cooled.
Pour the pie filling in a bowl and use a fork to smash the berries. Fold the container of Cool Whip into the pie filling.
Spread on top of the cooled cake. Sprinkle the diced strawberries on top. Keep the cake refrigerated until ready to serve.