Cranberry Lemon Sandwiches

Directions

1. In a large bowl, cream the butter, shortening and sugars until light and fluffy. Add eggs, one at a time, beating well after each addition. Beat in vanilla. Combine the flour, cream of tartar, lemon zest and salt; gradually add to the creamed mixture and mix well. Stir in cranberries. Cover and refrigerate for 2 hours or until easy to handle.
2. Roll into 1-in. balls. Place 2 in. apart on ungreased baking sheets. Flatten with a glass dipped in sugar. Bake at 350° for 12-14 minutes or until edges are lightly browned. Remove to wire racks to cool.
3. In a small bowl, combine the filling ingredients; beat until smooth. Spread on the bottoms of half of the cookies; top with remaining cookies.