Using a mixer, beat butter and sugar at medium speed until fluffy. Add in the egg and vanilla and mix until blended. Add flour and baking powder to the butter mixture. Stir until incorporated. Stir in dried cranberries.
Form dough into logs aprox 2 ½” inches diameter.
Wrap in parchment paper or wax paper and refrigerate until dough is firm, at least 2 hrs. (I often leave mine overnight.)
Heat oven to 350 degrees.
Remove dough from wax paper.
Place on a cutting board and using a sharp knife, cut into slices aprox ¼ inch thick.
Place dough about 1 inch apart on ungreased cookie sheet.
Bake for 8-10 minutes or until set, but not brown. Remove from cookie sheet. Cool on wire rack.