Using an electric mixer on medium speed or a whisk, beat the butter until smooth. Add the almond paste and beat until smooth. While continuing to beat, sprinkle in the sugar.
Add the eggs one at a time, beating well after each addition. Stir in the flour and set to one side.
Spread the jam evenly over the bottom of the baked pastry case. Spoon the almond paste mixture over the top of the jam and spread out evenly.
Sprinkle the surface evenly with the sliced almonds
Bake the tart until the filling is golden and the middle is firm to the touch, 35 to 40 minutes. Transfer to a wire rack and let the tart cool completely.