Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large mixing bowl, beat together the softened butter and granulated sugar on medium speed for about 3-4 minutes until light and fluffy.
Add the egg yolk, lemon juice, and lemon zest to the mixture and beat on low speed until well combined.
In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add to the wet ingredients, mixing until no streaks of flour remain.
Roll the dough into 1-inch balls and place them on the prepared baking sheet, spacing them 2 inches apart. Press a thumbprint into the center of each ball.
Fill each indentation with about 1/2 teaspoon of raspberry jam.
Bake for 12-15 minutes until golden along the edges and set in the center.
Cool on the baking sheet for 5 minutes before transferring to a wire rack. Dust with powdered sugar if desired.
Notes
These cookies are delightful with a cup of tea or coffee.