Preheat the oven to 350 F (175 C). Line two baking sheets with parchment paper.

Place the granulated sugar and lemon zest in a large bowl. Use your fingers to rub the lemon zest into the sugar, releasing the lemon oils.

Add the butter and brown sugar. Use a stand mixer or hand mixer to mix until well combined, about 2 minutes.

Add the egg and vanilla extract. Mix until well combined, until the dough looks lighter in color and slightly fluffy, about 1 minute.

Add the flour, salt, baking powder, and baking soda. Mix on low until just combined. Add the blueberries and use your hands to gently mix them in, trying not to burst any blueberries.

Use a large (1/4-cup) cookie scoop to scoop out the dough. Place up to 5 cookies on each baking sheet, spaced equally apart. Bake for 9-12 minutes, until the edges are just starting to brown. Let the cookies cool on the baking sheet for 15 minutes, then transfer to a cooling rack to cool completely.

While the cookies cool, make the topping. Place the heavy cream, mascarpone cheese, maple syrup, vanilla extract, and lemon zest in a large bowl. Use a stand mixer or hand mixer to mix until soft peaks form, about 3-5 minutes.

Dollop a few tablespoons of the cream on top of each cookie and enjoy! Keep any extra cookies in the fridge. Cookies will stay good for up to 2 days.