Start by making the tart crust, a tart pan (with a removable bottom) is best if you want to serve this with no pan or a pie pan will work fine if you want to serve it in a pan.
Preheat oven to 350F. In a food processor, combine the flour, sugar, salt, cinnamon and walnuts. Pulse until well combine and the walnuts are finely ground. Slowly add the butter in small pieces, making sure each piece is combined before adding the next.
The dough should be crumbly but sticks together well when pressed together. If dough is still too crumbly, add another tablespoon of butter.
Spray your pan with nonstick spray and press the dough into the bottom of the pan and up the sides. You want a consistent thickness of about ¼" throughout. Bake the crust for 20-22 minutes. The crust wont be golden but will smell like toasted nuts. Set crust aside and let cool.