Prepare the Baking Pan: Preheat your oven to 350°F (175°C). Line an 8×8-inch square baking pan with parchment paper, making sure the paper overhangs on two sides for easy lifting later. Lightly coat the parchment with nonstick spray to ensure a clean release after baking.
Grind the Almonds: Place the almonds in a food processor and pulse until they resemble fine crumbs, similar to coarse sand. This step enhances the nutty flavor and ensures even distribution throughout the dough.
Make the Shortbread Base: In a large mixing bowl, beat the softened butter, powdered sugar, and almond extract using a hand mixer for about 2–3 minutes, until the mixture becomes smooth, creamy, and slightly fluffy.
Combine Dry Ingredients: Add the flour and ground almonds to the butter mixture. Mix on low speed just until the dough begins to clump together. It should have a crumbly yet moist texture that can hold when pressed between your fingers.
Reserve the Crumble Topping: Scoop out about ½ cup of the dough, wrap it in plastic wrap, and place it in the refrigerator. This portion will be used as the crumbly topping for later.
Form the Crust: Press the remaining dough evenly into the bottom of your prepared pan, creating a smooth, firm layer. Use the back of a spoon or the flat bottom of a measuring cup to pack it tightly, ensuring no gaps remain.
Add the Raspberry Layer: Spread the raspberry jam over the crust in an even layer, leaving a slight border around the edges to prevent overflowing during baking.
Crumble the Topping: Remove the reserved dough from the refrigerator. Using your fingers, break it into small clumps and scatter them evenly across the jam layer, creating a rustic, crumbly top.
Bake to Golden Perfection: Place the pan in the preheated oven and bake for 45–50 minutes, or until the top turns a light golden brown and the jam layer is set without excessive jiggle in the center.
Cool and Slice: Allow the bars to cool completely in the pan on a wire rack. Once cooled, use the parchment paper overhang to lift them out. Cut into 9 even squares and serve.