Heat oven to 325^. Line a cookie sheet with foil or parchment paper.
Zest lemons trying to get 2 1/2 tablespoons of peel. Now juice them trying to get 3 tablespoons of juice.
Using food processor with knife blade; blend butter, sugar, & 1/2 cup powdered sugar until creamy. Add 2 tablespoons of zest & juice. Add flour & pulse until it comes together; add cranberries & pulse until blended.
With hand or spatula press dough evenly & thinly as posible in prepared pan. Can cut into bars or shapes at this time, this does not spread. Bake for 30 minutes or until edges are lightly brown. Cool in pan.
In small bowl mix 1 cup powdered sugar with 1/2 tablespoon zest & 1 tablespoon juice; until smooth. Can add 2 ounces of cream cheese. Add 1 teaspoon juice or water if necessary for spreading consistancy. Spread glaze evenly on shortbread, let set 10 minutes. Cut or break into bars.