Preheat oven to 350 degrees. Grease and flour 3 9-inch cake pans.
Using a hand mixer, combine cake mix, pudding, sour cream, eggs, oil, water, zest and lemon juice. Mix well.
Pour into prepared pans, dividing the batter equally into the prepared pans.
Bake for 40 min or until a toothpick when inserted comes out clean.
Allow the cakes to cool for 10 minutes in the pan then turn them out on a wire rack to cool completely.
Prepare the Fruit and Frosting
Take 4 -5 strawberries, slice them thin and add the tablespoon of sugar. Mi well. Set aside to be used when decorating.
Prepare mascarpone frosting while cake is baking.
Beat together the mascarpone cheese and powdered sugar. Add in the vanilla, salt and heavy cream. Whip until stiff peaks form. Place into refrigerator and chill until cake is cooled and ready to be frosted.
Assemble the Cake
Place one cake after completely cooled onto a cake disc or a plate.
Frost the top of the cake lightly and put 1 layer of strawberries that have been sitting in the sugar over the frosting. Repeat for next layer also.
Using the rest of the frosting start at the top working your way down the cake. Using the side of the knife take off excess icing to reveal the cake. This will give a naked cake effect.
Place extra strawberries and blueberries on top for decoration and sprinkle with sugar if desired.
Store this cake in an airtight container in the refrigerator.
The calories shown are based on the cake being cut into 15 pieces, with 1 serving being 1 slice of cake (all of the frosting used). Since different brands of ingredients have different nutritional information, the calories shown are just an estimate.