Preheat oven to 350 degrees F.  Grease and flour an 8-inch or 9-inch square pan.  Set aside.

In a medium bowl, stir flour, cream of tartar, baking soda, baking powder, and salt.  Set aside.

Using a standing or hand-held mixer, cream butter and sugar until light and fluffy.  Add eggs and vanilla.  Beat until combined.  On low speed, gradually blend in the dry ingredients until just combined.  Press 1/2 of the dough into the bottom of the prepared pan.  Sprinkle dough evenly with the Filling ingredients.  Drop teaspoon-sized amounts of remaining dough evenly over the Filling ingredients.*

Bake for 45 to 55 minutes or until bars are golden brown and a toothpick inserted in the center comes out clean.  Remove to a wire rack and allow to cool completely.

To Prepare Glaze:

In a small bowl, stir powdered sugar, 1 tbsp. milk, vanilla and cinnamon until smooth.  Gradually add milk by the teaspoon until thin enough to drizzle.  Drizzle glaze over cooled bars.  Cut into 12 or 16 bars.