Preheat the oven to 325°F (163°C). Line two baking sheets with parchment paper.
In a large bowl, cream the softened unsalted butter and powdered sugar together until light and fluffy using an electric mixer on medium speed.
Add the salt and gradually mix in the all-purpose flour until the dough just comes together. Do not overmix.
Turn the dough onto a lightly floured surface and gently knead it a few times to form a smooth ball.
Roll out the dough to about 1/4 inch (6 mm) thickness.
Using a 2-inch (5 cm) round cookie cutter, cut out circles and place them on the prepared baking sheets about 1 inch apart.
Bake the cookies in the preheated oven for 20 to 25 minutes or until the edges are lightly golden.
Remove the cookies from the oven and allow them to cool completely on the baking sheets.
Once cooled, spread about 1 teaspoon of raspberry jam onto the flat side of half of the cookies.
Top each jam-covered cookie with another cookie, flat side down, to create a sandwich.
Press gently to spread the filling evenly and serve.