For the crust: Combine flour, powdered sugar and salt, then cut the cold butter into the dry ingredients with a fork or pastry blender until the butter is the size of small peas. Press the mixture into the bottom of a 9x13 inch pan and bake for 12 to 14 minutes. It should just be starting to turn brown.
Berry Filling: While the crust is cooking, heat the jam in a small sauce pan on medium low heat to melt and make it easy to spread. Gently spread the melted jam over the warm crust. Mix the raspberries with a couple tablespoons of flour and sprinkle them over the jam layer.
Streusel Topping: Mix together the brown sugar and flour then cut in the butter until you have a crumbly mixture. Sprinkle over the raspberry layer.
Bake for 25 to 30 minutes. Cool before cutting into squares. This pan will make 24 good sized bars. You can cut this recipe in half and put it into an 8x8" pan. Store in the fridge, remove from the fridge one hour before serving.
Recipe by at https://sufficientacres.com/2016/06/21/fresh-raspberry-dessert-bars/