Line baking sheets with parchment paper. Beat the softened butter and granulated sugar for 2–3 minutes, until light and creamy.

Beat in the egg yolk and vanilla until evenly combined. Add the flour and salt gradually, mixing only until a soft dough forms.

Cover the dough and refrigerate it for 30–60 minutes. Chilling helps the cookies hold their shape and reduces spreading.

Scoop about 1 tablespoon of dough for each cookie and roll it into a ball. Arrange the balls about 2 inches apart on the prepared baking sheets.

Press a small indentation into the center of each dough ball with your thumb or the rounded end of a measuring spoon. Fill each hollow with approximately 1/2 teaspoon of raspberry jam, taking care not to overfill.

Bake at 350°F (175°C) for 10–13 minutes, rotating the pan halfway through if needed. Remove the cookies when the edges are set and lightly golden while the centers still look somewhat soft.

Cool the cookies on the baking sheet for 5–10 minutes, then transfer them to a wire rack. Once fully cooled, dust with confectioners’ sugar if desired.