1. Place 1 cup flour and the pecans in a food processor; pulse until nuts are finely ground. Transfer to a medium bowl. Whisk in remaining 1 cup flour and the salt.
2. Beat together butter, 1/2 cup sugar, the zest and extract in a large bowl on high speed until light and fluffy, about 2 minutes. Reduce speed to low and slowly add flour-nut mixture, beating until just combined. Chill dough until firm but still pliable, about 1 hour.
3. Preheat oven to 350 degree F and arrange racks in upper and lower thirds; lightly butter 2 large cookie sheets.
4. Using a 1-1/8-inch ice-cream scoop, drop dough onto prepared cookie sheets. Roll each between palms of hands to form smooth balls. Arrange on cookie sheets, placing about 1 inch apart, and chill until firm, about 15 minutes.
5. Bake cookies until bottoms are golden brown, switching sheets halfway through, about 15 minutes. Transfer cookies on sheets to racks and let stand until just cool enough to handle but still warm, about 4 minutes.
6. Place remaining 2 cups sugar in a bowl. Working with 4 cookies at a time, roll in sugar, coating well. Transfer to rack and cool completely. Roll cooled cookies in sugar one more time. (Can be stored at room temperature in an air-tight container, in single layers separated by waxed paper, up to 2 weeks.) Makes about 30 cookies.