Preheat the oven to 325°F (163°C). Line two baking sheets with parchment paper.
In a large mixing bowl, cream together the softened unsalted butter and granulated sugar until light and fluffy, about 3-5 minutes.
Add the vanilla extract and mix until combined.
Gradually add the all-purpose flour and salt to the butter mixture, mixing on low speed until the dough just comes together.
Divide the dough in half. Roll out one half on a lightly floured surface to about 1/4 inch thickness.
Using a round cookie cutter (about 2 inches in diameter), cut out half of the cookies. Place them on the prepared baking sheets.
Roll out the second half of the dough and cut out the same number of cookies with a slightly smaller round cutter or use the same size and then cut a small circle in the center of each cookie to create a window for the jam.
Place the cut-out cookies on the baking sheets.
Bake the cookies for 15-18 minutes, or until the edges are lightly golden. Remove from the oven and let cool completely on the baking sheets.
Spread about 1/2 teaspoon of raspberry jam on each whole cookie base.
Top each jam-covered cookie with a cut-out cookie to form a sandwich, gently pressing down to seal.
Allow the cookies to set for 10 minutes before serving.