Sift together the dry ingredients in a small mixing bowl: whole wheat flour, all-purpose flour, baking powder, baking soda, and salt.
Set aside ½ teaspoon of the lemon zest (to be used later in the lemon cream).
In a separate large mixing bowl, whisk together the yogurt, canola oil, ⅔ cup granulated sugar, egg, 1 teaspoon vanilla extract, and all of the remaining fresh lemon zest. Slowly add the flour mixture to the yogurt mixture, stirring until everything is well combined.
Scoop tablespoons of batter onto a parchment-lined baking sheet. Allow a few inches of space surrounding each scoop (six scoops of batter per baking sheet) Bake for about 9-11 minutes, or until a toothpick inserted into the center of a cakes comes out clean.
Meanwhile, in a mixing bowl, combine the Neufchâtel low-fat cream cheese, ½ cup granulated sugar, the water and 1 teaspoon vanilla extract. Add the ½ teaspoon of fresh lemon zest set aside earlier. Using a handheld mixer, set on low speed, blend the ingredients into a smooth, creamy frosting.
Arrange half of the baked cakes on a clean counter and use a spatula to spread a thin layer of the cream cheese mixture all over the flat side of each cake. Top with handfuls of fresh blueberries and diced strawberries.
Cut a sheet of lined or computer paper into a square slightly larger than the size of the cakes. Use a cookie cutter to trace the shape of a star in the center of the paper. Fold the paper in half to cut into the center of the star. Unfold and cut out along the tracing, creating a star cut-out in the center of the square.
Arrange the star over the center of one cake half.
Place about ¼ cup of powdered sugar in a fine mesh strainer. Hold the strainer of powdered sugar over the cake and lightly tap it, allowing the "snow" of powdered sugar to fill in every inch of the star shape. Very carefully lift the paper off the cake and tap off any excess sugar until the paper is clean. Repeat until all cake tops have a star.
Top off each frosted and berried-filled cake bottom with a star top, and serve.
Storage: cakes should be stored in a covered container at room temperature in a cool, dry spot. Lemon cream and berries should be stored separately in covered containers and refrigerated. Frost cakes immediately before serving.