Preheat your oven to 350°F (175°C) and line a 9×13-inch baking pan with parchment paper.

In a large mixing bowl, cream together the softened butter and granulated sugar until fluffy and pale.

Add the egg, vanilla extract, and almond extract; mix until smoothly combined.

In a separate bowl, whisk together flour, salt, and optionally the ground almonds. Fold this mixture into the wet ingredients.

Press about ⅔ of the dough into the bottom of the prepared pan.

Bake for 12-15 minutes until the edges are set; allow to cool briefly.

Stir raspberry jam to soften and mix in lemon zest if using.

Spread the jam over the cooled crust evenly.

Crumble the remaining dough over the jam layer.

Sprinkle sliced almonds over the top.

Bake for an additional 25-30 minutes until golden and jam is bubbling.

Allow to cool completely for at least 2 hours before cutting into bars.