In a medium bowl, whisk together flour, cinnamon, baking powder, and salt. Set aside.
In a large bowl, beat butter and sugar on high speed until smooth and creamy, about 2 minutes.
Add egg and vanilla extract, and beat on high speed until combined, about 1 minute. Scrape sides and mix again if needed.
Gradually add dry ingredients to wet ingredients and mix on low speed until combined. If dough is too soft, add 1 tablespoon flour.
Divide dough into two equal parts. Roll each between lightly floured parchment or silicone mats to 1/4-inch thickness.
Stack the dough sheets with parchment between, cover, and refrigerate for 1-2 hours or up to 2 days.
Preheat oven to 350°F (177°C) and line baking sheets with parchment or mats.
Cut chilled dough into shapes with cookie cutters. Re-roll scraps and continue until all dough is used.
Place cookies 1-2 inches apart on baking sheets and bake 9-10 minutes until edges are lightly browned, rotating halfway.
Cool cookies on baking sheets 5 minutes, then transfer to wire rack to cool completely before decorating.
Prepare icing and tint with gel food coloring if desired. Dip cookies in icing and add sprinkles. Let icing set before storing or gifting.