Preheat your oven to 350°F. While it heats, divide the sugar cookie dough into 24 equal pieces and roll each into a small ball. Place them on baking sheets, spacing them about 2 inches apart—they'll spread slightly as they bake. Bake for 10-12 minutes until the edges are lightly golden but the centers still look slightly underbaked; this keeps them soft and chewy rather than crispy. Remove from the oven and let the cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.
While the cookies cool, prepare the frosting by combining the softened cream cheese, sifted powdered sugar, vanilla extract, and a pinch of salt in a bowl. Mix until completely smooth and creamy, scraping down the sides of the bowl as needed. I like to sift the powdered sugar before measuring to avoid lumps in the frosting—it makes a big difference in texture. If you're using lemon zest for brightness, fold it in now.
Rinse and dry your mixed berries thoroughly—any excess moisture will make the cookies soggy. Leave small berries like blueberries or raspberries whole, and slice larger berries like strawberries into thin, even pieces so they look neat on top. Arrange them on a plate or cutting board, ready to use.
Once the cookies are completely cool, spread or pipe about a tablespoon of the cream cheese frosting from Step 2 onto the top of each cookie base, creating a small mound or smooth layer. I like to use a small offset spatula or the back of a spoon to create an even, slightly raised surface—this gives you a nice base for the fruit to sit on. Top each pizza with an arrangement of the prepared berries from Step 3, pressing them gently into the frosting so they stick. Serve immediately or refrigerate for up to 4 hours until serving.