In a large bowl, combine the sugar, pumpkin pie spice, salt, pumpkin puree, sour cream, and 1 egg. Beat on low speed until smooth, or beat with wire whisk.
Using 3-inch cookie cutters, cut the pie dough into 8 bottoms and 8 tops. Spoon 1 tablespoon of filling on the bottom pie dough cut outs (about ½-inch from the edge). Wet the edges of the bottom dough with water. Top with the top pie dough cut outs and fork the edges to seal. Continue with the remaining tarts.
Mix the remaining egg with 1 tablespoon of water in a small bowl. Brush the tops of the tarts with the egg-water mixture. Bake on a parchment covered baking sheet for 12-13 minutes until the filling is just set. Optional: sprinkle the tarts with coarse sugar before baking if desired.