Heat the raspberry jam, cornstarch, and lemon juice together in a small saucepan over medium heat. Stir frequently until the mixture thickens, then allow it to cool completely before using.

In a mixing bowl, cream the softened unsalted butter and granulated sugar together until light and fluffy, about 3 to 5 minutes.

Add the vanilla extract and mix until just combined.

Gradually add the all-purpose flour and salt to the butter mixture. Mix until just incorporated.

Prepare a clean, lightly floured surface and roll out the dough into rectangular shapes.

Spread the cooled raspberry mixture evenly over the surface of each rolled rectangle.

Starting from one end, roll each rectangle into a log shape using parchment paper to guide.

Wrap the logs tightly in plastic wrap and refrigerate for at least 1 hour.

Preheat your oven to 350°F and line baking sheets with parchment paper.

After the logs have chilled, slice them into 1/4-inch rounds and lay them flat on the prepared baking sheets.

Bake for 12 to 15 minutes, watching closely for the edges to turn golden.

Remove from the oven and let cool briefly on the baking sheets before transferring to a wire rack.