1. Preheat your oven to 325°F (163°C) and line a 9×9-inch square baking pan with parchment paper, leaving an overhang on the sides for easy removal of the baked cookies.

2. In a large mixing bowl, cream the softened butter and granulated sugar together until light and fluffy, about 3-4 minutes. Beat in the vanilla extract until well combined.

3. In a separate bowl, whisk together the flour and salt. Gradually add the flour mixture to the butter mixture, mixing on low speed until the dough just comes together. Be careful not to overmix.

4. Press two-thirds of the shortbread dough evenly into the prepared baking pan, creating a smooth, compact base layer. Warm the raspberry jam slightly in the microwave for 10-15 seconds to make it easier to spread, then spread the jam evenly over the pressed dough layer.

5. Crumble the remaining dough over the jam layer, leaving some gaps for the raspberry to show through.

6. Bake the Raspberry Swirl Shortbread Cookies for 35-40 minutes, or until the top is lightly golden brown and the edges are set. Allow the cookies to cool completely in the pan before lifting them out using the parchment paper overhang.

7. Once cooled, use a sharp knife to cut the shortbread into squares or rectangles. Dust the cookies with powdered sugar, if desired, for a touch of sweetness and a beautiful presentation.