Step 1: Prepare the Cookie Dough

1. In a large bowl, beat the butter and sugar together until light and fluffy.
2. Add the egg and vanilla extract, and continue mixing until well combined.
3. Gradually add the flour and salt, mixing until the dough comes together.
4. Shape the dough into a ball, wrap it in plastic wrap, and refrigerate for at least 30 minutes (this helps firm up the dough for easy rolling).

Step 2: Roll and Cut the Cookies

1. Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
2. Lightly flour a clean surface and roll out the dough to about 1/8 inch thick.
3. Use a round or heart-shaped cookie cutter to cut out an even number of cookies.
4. For half of the cookies, cut out a small hole or shape in the center (these will be the tops).

Step 3: Bake the Cookies

1. Arrange the cookies on the prepared baking sheet, leaving some space between them.
2. Bake for 8-10 minutes, or until the edges are lightly golden.
3. Remove from the oven and let the cookies cool on a wire rack.

Step 4: Prepare the Raspberry Filling

1. In a small bowl, mix raspberry jam with lemon juice (if using).
2. Heat the jam slightly for easy spreading (optional but recommended).

Step 5: Assemble the Cookies

1. Spread about 1 teaspoon of raspberry jam on the flat side of each whole cookie.
2. Place a cut-out cookie on top, gently pressing to form a sandwich.
3. Optionally, dust the top cookies with powdered sugar for a classic look.