Heat oven to 350°. Spread pepitas onto a baking sheet. Bake at 350° for 10 minutes, until toasted.
Combine 1 cup of the flour and the toasted pepitas in a food processor; pulse until pepitas are finely ground. Transfer to a bowl and whisk in remaining 1 cup flour, the salt and cardamom, if using.
In a large bowl, beat butter, 3/4 cup of the confectioners' sugar and the vanilla on high speed until light and fluffy, 2 minutes. Reduce speed to low; slowly add flour-nut mixture, beating just until combined.
Shape dough into 1-inch balls between your palms and place 1 inch apart on baking sheets. Bake at 350° for 15 minutes or until bottoms just begin to brown. Transfer cookies to racks and let cool slightly, about 4 minutes.
Place remaining 1 cup confectioners' sugar in a bowl. Working with 4 cookies at a time, roll in sugar, coating well. Transfer to a rack, let cool completely and roll again in sugar.
