For the crust, whisk together the flour, sugar, almonds, cinnamon and salt in a medium-size bowl. Place the butter in the bowl and, using your fingers, rub the butter into the flour mixture until it looks crumbly. Add the egg yolk and the lemon juice and mix with a fork until it is incorporated. The dough will be very crumbly at this point. Place the dough on a floured countertop. Push through the dougha couple of times until you can form a rough ball. Flatten into a disk. Place the disk in plastic wrap or wax paper and refrigerate for 15–20 minutes.
In another medium bowl place the mulberries, sugar, flour, zest, orange and lemon juices. Mix gently with a spoon. Allow to sit while the crust is chilling. Preheat oven to 400˚. Remove the crust dough from refrigerator. Place on a piece of parchment paper and put the wax or plastic wrap back on top. Take a rolling pin and roll the dough away from you. Turn the whole thing a quarter turn, roll away from you again. Continue this process of rolling once and then turning until you have a nice round piece of dough about 9–10 inches across. Remove the plastic wrap.
Place the fruit mixture in the center of the tart and spread it out, leaving about 2 inches all the way around the crust. Gently pull the crust up over the fruit. It will be crumbly and so you will need to repair it in places to get it to make an edge. If you need to close up any small holes, use a bit of water on your finger and smooth it over the broken area to close it up. Don’t be concerned with perfection. This is a rustic tart and should look that way. Sprinkle the almonds over the middle of the tart.
Pick up the parchment paper with the tart on top and place the whole thing (paper and all) in a pie plate. Place in oven and bake for 35–40 minutes. The crust should be golden and the center should be bubbly. Allow to cool completely and then remove from the pie plate. Place on a serving dish and sprinkle with powdered sugar.