Preheat oven to 375 degrees F. Let piecrust stand according to package directions. Meanwhile, for filling, in a medium bowl combine egg, pumpkin, and half-and-half. Stir in sugar, flour, spice, lemon peel, vanilla, and salt.
Unroll crusts. Using a 2 1/2-inch round cutter, cut out 24 circles. (Reserve scraps to repair any tears.) Press circles into twenty-four 1 3/4-inch muffin cups. Spoon about 1 tablespoon of the filling into each pastry-lined muffin cup. If desired, place a pecan half on top of each tartlet.
Bake about 25 minutes or until filling is set and pastry is golden. Cool in muffin cups on a wire rack for 5 minutes. Carefully remove from muffin cups and cool completely on wire rack. Store in an airtight container in the refrigerator within 2 hours of baking.