Sugar Cookie Crust

1. Preheat the oven to 375 degrees.
2. Cream together butter and sugar either with a large stand mixer or a hand mixer.
3. Add in egg and vanilla and mix till combined.
4. Add the flour, salt, and baking powder to the bowl. Mix till combined - the mixture will be crumbly.
5. Line a 9x13 baking sheet with parchment paper. Place the dough onto the paper. Using your fingers and hands, press the dough out evenly and firmly in the pan, making sure to get to each corner and not have any uneven spots, the best you can. 
6. Bake for 10 minutes until just barely browned on the edges.
7. Remove from oven and let cool completely before frosting.

Cream Cheese Frosting

1. In a stand mixer or with a hand-held mixer, cream together the softened cream cheese and butter. Mix for 2-3 minutes, making sure all lumps are out, and it is nice and smooth.
2. Slowly add powdered sugar, 1/2 cup at a time. Scrape down sides with a spatula in between each addition. Add lemon juice and salt at the end and mix well.

To Assemble

1. Remove the crust from the pan by lifting up the parchment paper. Remove the paper and place it on a serving platter.
2. Spoon frosting onto the cooled cookie and spread evenly with an offset spatula. This can also be done with a piping bag and a large hole opening, if desired as well.
3. Arrange the blueberries and strawberries in a flag pattern. 
4. Serve immediately or place in the fridge to chill until needed (serving within the next couple of hours).