Make the shortcrust pastry in a food processor (or make it in a bowl like for regular pastry) combine all the filling ingredients and whiz until it just comes together into a dough. Don't clean out the food processor bowl as you'll use it for the filling.
Use about a third of the dough and roll into into a finger thick rope. Place the rope around the inside perimeter of a 9-inch (23cm) fluted tart pan with a removable bottom or a deep-dish 9-inch pie pan. Press the rope of dough against the edges of the pan to make a raised 1-inch (2.5cm) crust. Then crumble in large chunks of the remaining shortcrust pastry evenly over the bottom of the tart pan and press it down evenly with your fingers to form a thick crust. Patch any holes or thin spots with pastry so it is evenly filled in. Use a smooth-bottomed measuring cup or glass to press the dough out more smoothly and evenly and to press out the dough all around the edge where the dough goes up the side of the pan so it isn't overly thick along the fold. Run a knife all along the top edge of the crust to trim off any excess dough sticking up above the rim.
Prick the dough all over the bottom of the tin with a fork (this is called docking and prevents it from buckling). Line it with a piece of parchment paper that sticks up a bit over the edge of the pan and fill the paper with baking weights (dried beans or ceramic or metal pie weights). Bake for 15 minutes with the weights (this is called blind baking). Then remove the weights using the edges of the paper to lift them out. Bake the crust for another 5 minutes without the weights to dry it out a bit more.
While the crust is baking, make the filling. In the unwashed food processor canister (or in a bowl with a mixer or wooden spoon), blend the butter and sugar until fluffy. Add the almond flour, salt, eggs, and almond extract (or lemon zest). Whiz until a smooth paste forms.
When the crust is finished baking, spread the jam in the bottom of the crust. Spoon the filling evenly on top of the jam in dollops, then use an offset spatula or the back of a spoon to carefully spread the filling around and right to the edges of the pan, without disturbing the jam too much. Smooth the top and sprinkle it with the almonds.
Bake for 35 to 40 minutes.
Allow the tart to cool before cutting into 8 wedges. Serve with whipped cream.
Notes
*Although raspberry jam is traditional in a Bakewell tart, any red jam would work, or even a luscious apricot or peach jam.*If you don't have almond flour, grind up whole, sliced, or slivered blanched almonds in the food processor until fine.