- Preheat the oven to 400 degrees F.
- In the bowl of a food processor, combine the walnuts and 3 tablespoons of the flour. Pulse to a medium-fine grind, not too fine. Transfer to a large bowl and set aside.
- Combine the remaining flour, the salt, sugar, cinnamon, and butter in the bowl of a food processor, and pulse until the mixture resembles coarse crumbs. Add this mixture to the walnuts and lightly mix the dough with a wooden spoon or your hands. Stir in the eggs and zest and gently press the dough into a disc.
- Set aside one-quarter of the dough for the top. Press the remaining dough into the pan, taking care to make the sides of the tart no more than 1/4 inch thick because the crusts get very firm when baked.
- Place the tart pan on a flat baking sheet and bake for 15 minutes.
- While the tart bottom is baking, gently roll out the remaining dough on a lightly floured surface, using a lightly floured rolling pin, to a thickness of 1/4 inch. Using a variety of round cookie cutters in different sizes, cut out polka dots, about 12 to 15 circles, depending on their size. If the dough becomes soft, tansfer the circles to wax paper or parchment paper, and chill them to make handling easier. Set the leftover dough aside to suse for cookies (see Notes in Additional Info) or discard.
- Remove the tart pan from the oven and set on a cooling rack.
- Lower the oven temperature to 350 degrees F. Lightly sprinkle the bread crumbs or graham cracker crumbs over the bottom of the tart shell. This prevents the crust from becoming too soggy, and keeps the jam from sliding around. Spread the jam evenly over the tart crust. Top the jam with polka dots in random pattern, leaving about 2 inches of jam showing between the dots.
- To make the glaze, mix the yolk and water, and lightly brush each polka dot and the top of the tart shell. Return the tart to the oven and bake for 1 hour. The polka dots and the tart shell will be a rich golden brown and the polka dots will be completly baked. Cool completely in the pan on a cooling rack. Carefully remove the outer ring of the tart pan. Serve with ice cream, whipped cream, or crème fraîche, if desired.