Preheat oven to 425 degrees.

Prepare sunflower seed pastry dough according to recipe.

Roll out the dough 1/8-inch thick on a lightly floured surface.

Cut out 6 rounds using a 4 1/2 -inch round cutter.

Press each round into a fluted metal tartlet pan, 3 1/4 inches across the bottom and 5/8-inch deep.

Prick the shells lightly with a fork and refrigerate for 30 minutes or freeze for 15 minutes.

Line the shells with foil, fill with raw rice or beans for weighting.

Bake the shells in a jelly-roll pan in the lower third of the oven for 15 minutes.

Remove the rice and foil carefully.

Bake the shells for 5 to 7 minutes more, until golden brown.

Let the shells cool in the pans on a rack.

The shells may be made one day in advance and stored in an airtight container at room temperature.

Reduce the oven temperature to 375 degrees.

Prepare the butternut squash filling.

In a food processor or bowl with a whisk, blend the pureed butternut squash with the heavy cream, egg, sage, salt, pepper, and cayenne.

Divide the filling evenly among the tartlet shells, smoothing it.

Arrange 6 strips of Gruyere, trimming them to fit, in a lattice pattern on each tartlet.

Bake the tartlets in a jelly-roll pan in the middle of the oven for 20 to 25 minutes, or until the filling is puffed slightly and the cheese is melted.

Serve immediately.