In a food processor, combine flour, cold cubed butter, sugar, and salt. Pulse until mixture resembles coarse crumbs.
Press the dough into a 9-inch tart pan with a removable bottom. Prick the bottom with a fork and bake for 15-20 minutes until lightly golden. Let cool.
Spread raspberry jam evenly over the cooled crust.
Arrange fresh raspberries on top of the jam.
In a heatproof bowl, combine chopped dark chocolate and 1 tablespoon of butter.
In a small saucepan, heat the heavy cream until it just starts to simmer.
Pour the hot cream over the chocolate and butter. Let sit for 2 minutes then stir until smooth and glossy.
Pour the chocolate ganache over the raspberries in the tart shell. Smooth the top with a spatula.
Chill the tart in the refrigerator for at least 2 hours until the ganache is set.
Slice and serve the chocolate raspberry tart. Enjoy!