Preheat the oven: Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
Cream the butter and sugar: In a large bowl, cream together the softened butter and granulated sugar until light and fluffy (about 3-5 minutes).
Add egg and vanilla: Beat in the egg and vanilla extract until fully incorporated.
Mix dry ingredients: In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Infuse lemon flavor: Stir in the lemon zest and lemon juice for a bright, zesty flavor.
Shape the dough: Roll the dough into 1-inch balls and place them on the prepared baking sheet, spacing them about 2 inches apart. Lightly flatten each ball with your palm.
Bake: Bake for 10-12 minutes, or until the edges are lightly golden. Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack.
Assemble the sandwiches: Spread raspberry jam on the flat side of half the cookies. Top with the remaining cookies to create sandwiches.
Add final touches: Sprinkle granulated sugar on top for an extra touch of sweetness.