in a food processor, combine the flour and butter.
Process in an off/on pulses until mixture is the consistency of fine crumbs.
In a small bowl, beat together the egg yolk, vanilla, sugar, lemon zest and salt until well blended. Pour the egg yolk mixture over the flour mixture and process in off/on pulses until just evenly incorporated and smooth.do not overprocess. divide the dough into quarters.
Divide each quarter into 6 equal portions. Shape the portions into balls with lightly greased hands.
Flatten each ball slightly. Place each ball in a muffin cup; press down in the center so dough fits cup snugly and is slightly concave.
Set the muffin tins on a baking sheet. Preheat oven to 350 -- *.
Bake in the upper third of the oven for 16-19 minutes, or until lightly browned all over and slightly darker at the edges.
Transfer the baking sheet with the muffin pans to wire racks.
in a food processor, process the cream cheese, sugar, egg, lemon zest, lemon juice and vanilla until well blended and completely smooth.
Transfer the filling to a 2 cup measure with a spout.
Pour the filling over the baking dough rounds, dividing it evenly among the muffin cups. bake in the upper third of the oven for 10-12 minutes or until the filling is set and just beginning to color at the edges. Add more 1/4 tsp jam or preserves to the center of each tassie and continue baking until the filling is puffed and slightly tinged with color. 4-5 minutes more.
Transfer the muffin pans to wire racks. Let stand until completely cooled. Refrigerate in an airtight container for up to 1 week or freeze for up to 1 month.filli.