1. Prepare the Raspberry Swirl

• In a small bowl, mix raspberry jam, cornstarch, and lemon juice until smooth. Set aside.

2. Make the Shortbread Dough

• In a large bowl, cream the butter and sugar with an electric mixer until light and fluffy.
• Add the vanilla extract and mix until combined.
• Gradually incorporate the flour and salt, stirring just until the dough forms.

3. Layer the Dough

• Divide the dough into two portions. Roll each into a 1/4-inch-thick rectangle between parchment paper.
• Spread a thin layer of the raspberry mixture evenly over one rectangle, leaving a 1/4-inch border.
• Place the second rectangle on top of the raspberry-coated dough.

4. Roll and Chill

• Starting at one short end, roll the dough into a tight log.
• Wrap the log in plastic wrap and refrigerate for 1-2 hours until firm.

5. Slice and Bake

• Preheat the oven to 350°F (175°C). Line baking sheets with parchment paper.
• Slice the chilled log into 1/4-inch rounds. Arrange them 2 inches apart on the baking sheets.
• Bake for 10-12 minutes, or until the edges are lightly golden.
• Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack.