Maple Butter Tarts

Combine flour and salt in the bowl of a food processor and pulse to combine. Add butter and pulse until the largest pieces are the size of peas and some pieces are tiny.
Add 3 tablespoons of water and pulse again. Squeeze a handful of the crumbs together to see if it holds. If not, add the water in small increments. You do not want the dough to come together in a ball in the processor. Once the dough holds together without too much effort, flatten it into a disc and wrap in plastic. Refrigerate for a few hours.
Let dough sit at room temperature for a few minutes, then roll on a lightly floured surface to 1/8" thickness. Cut circles using a 4.5" round cutter. Place in standard (1/2) cup muffin tin. Chill for 30 minutes.
Preheat oven to 400F and place a rack in lower third of oven. Cream butter and brown sugar and add egg. Mix well, then add syrup, vanilla, salt and lemon juice.
If you are using any nuts, raisins or berries, add a few to each pastry shell. You only want enough to barely cover the bottom of the shell. Add syrup mixture, filling only 3/4 full. Don't be tempted to fill them to the top, as they'll bubble over and stick to the pan.
Bake for 13-15 minutes, until filling is bubbly and puffy and pastry is golden. Cool on a rack for 5 minutes, then run a knife around each tart and carefully remove. You must remove them when they are warm, or else they will weld themselves to the pan. Cool and enjoy slightly warm or at room temperature.