Preheat the oven to 350°F (175°C). Line a 9×9-inch square baking pan with parchment paper, leaving an overhang on two sides for easy removal.
In a large bowl, cream together the softened butter and granulated sugar using an electric mixer on medium speed until light and fluffy, about 3 to 4 minutes.
Add the all-purpose flour and salt to the butter mixture. Mix on low speed until the dough just comes together and no dry flour remains.
Press two-thirds of the dough evenly into the bottom of the prepared baking pan to form the base layer.
Spread the raspberry jam evenly over the shortbread base layer.
Crumble the remaining one-third of the dough over the jam layer, covering it as evenly as possible.
Bake in the preheated oven for 30 to 35 minutes, or until the top is lightly golden and set.
Remove from the oven and allow the bars to cool completely in the pan on a wire rack.
Once cooled, use the parchment paper overhang to lift the bars out of the pan. Cut into 16 squares and serve.