Step 1Combine the flour, sugar and salt in a bowl. Cut in the butter with a pastry blender or a fork until the crust is crumbly. Sprinkle the water over the flour mixture. Stir with a fork until the dough comes together into a ball. Wrap in plastic wrap and chill for 30 minutes. Separate the dough into 4 parts. Roll out one part of the dough on a lightly floured surface into a round to fit into 4-inch round tart pan with a removable bottom. Repeat with the remaining dough.
Step 1Combine the flour, sugar, vanilla and salt in a bowl. Add the butter and marzipan, and work into the dough with a pastry blender or fork until crumbly. Set aside.
Step 1Heat the oven to 400 degrees.
Step 2Combine the sugar, flour, rhubarb, raspberries and lemon juice in a bowl. Gently stir until combined. Divide the filling among the tart shells.
Step 3Sprinkle the crumb topping over the top of each. Place the tarts on a baking sheet and bake about 30 minutes until browned and bubbly. Remove from oven and let cool to warm before serving.