Preheat Oven and Prepare Baking Sheets:

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

Make the Lemon Cookie Dough:

In a large mixing bowl, beat the softened butter, granulated sugar, and lemon zest together until light and fluffy. Add the lemon juice and vanilla extract, mixing until combined.

In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until a soft dough forms.

Shape and Bake the Cookies:

Roll the dough into small balls (about 1 tablespoon each) and place them on the prepared baking sheets, spacing them about 2 inches apart. Flatten each ball slightly with the back of a spoon or your fingers.

Bake for 10–12 minutes, or until the edges are just lightly golden. Let the cookies cool completely on a wire rack.

Prepare the Blueberry Cream Filling:

In a small saucepan, combine the blueberries, granulated sugar, and lemon juice. Cook over medium heat until the blueberries burst and the mixture thickens (about 5 minutes). Remove from heat, strain to remove skins, and let cool completely.

In a mixing bowl, beat the softened cream cheese, powdered sugar, and vanilla extract until smooth. Add the cooled blueberry sauce and mix until well combined.

Assemble the Sandwich Cookies:

Spread a dollop of blueberry cream filling onto the flat side of one cookie. Top with another cookie to create a sandwich. Repeat with the remaining cookies.

Chill and Serve:

Refrigerate the assembled cookies for 30 minutes to allow the filling to set. Serve chilled or at room temperature.