Cream butter and sugar together until light and fluffy, about 2-3 minutes.

Beat in egg and vanilla, about 1 minute.

In a separate bowl, mix flour, baking powder, and 1 tsp cinnamon. Add the dry mixture to the butter/sugar mixture and stir to just combine into a cohesive dough (do not overwork).

Chill dough for 30 minutes.

While the dough is chilling, preheat the oven to 350 degrees F (175 C).

Mix the topping by combining sugar and cinnamon.

Remove the dough from the refrigerator and form it into about a dozen walnut-sized balls.

Roll each ball in the cinnamon/sugar mixture until coated on all sides, and then place 3 inches apart on a cookie sheet.

Bake 12-15 minutes until just set in the center. Remove from the oven and allow the cookies to cool completely on the trays (do not remove to a cooling rack). This ensures they're fully cooked in the center, without over-baking.

Once cool store in an airtight container for up to a few days, or freeze for longer storage.