Prepare Baking Pan:Line a 9x13-inch baking dish with a long strip of parchment paper, ensuring the edges hang over the sides to help lift out the bars later. This will prevent sticking and make removal effortless.
Make the Almond Crust:In a food processor, combine the almond paste and softened butter. Pulse until smooth and creamy. Add the sugar and egg, then process again until fully blended. Gradually add the flour, baking powder, baking soda, and salt, pulsing until the mixture forms a soft, cohesive dough. Press this dough evenly into the bottom of the prepared pan, creating a firm base.
Prepare Raspberry Filling:In a bowl, whisk the raspberry jam until smooth. Gently fold in the fresh raspberries, carefully coating them with the jam without breaking the berries. Spread this fruit mixture evenly over the almond crust layer.
Make the Crumb Topping:In a separate bowl, combine the flour, oats, brown sugar, and sliced almonds. Pour the melted butter over the dry ingredients and stir with a fork until coarse crumbs form. Evenly sprinkle this crumb mixture over the raspberry layer.
Bake the Squares:Place the baking dish in a preheated oven at 350°F (175°C). Bake for 40 to 45 minutes, or until the topping turns a light golden brown and the filling is bubbling slightly at the edges.
Cool and Slice:Remove the pan from the oven and transfer it to a wire cooling rack. Let the fruit squares cool completely in the pan. Once cooled, use the parchment paper edges to lift the entire block out of the pan. Place it on a cutting board and slice into 20 to 24 squares.