Beat the butter and sugar for 2 minutes at medium-high speed until it is smooth and creamy. Scrape the bowl and add the egg, vanilla, and cinnamon, beating on medium-high for about 30 seconds. Add the flour and blend on low speed for about 20 seconds. Wrap the dough in plastic wrap and chill for 1 hour. Preheat a conventional oven to 325 °F or a convection oven to 310 °F, placing the oven racks so they divide the ovens into thirds. Line baking sheets with parchment. Roll the dough 1/4" thick. Cut into desired shapes with sharp cookie cutters. Place the cookies on the lined baking sheets. Brush with the egg white mixture and sprinkle with colored sugar. Bake in the preheated oven 10-12 minutes, rotating the pans halfway through the baking time until just starting to feel firm. Remove the pans from the oven and rest them on wire racks to cool. When the cookies are completely cool, store them in an airtight container for up to 4 weeks.
Chef's Note: Everyone expects to see cutouts for the holidays, and this is a delicious departure from the plain sugar cookies most often made. They are lightly scented with cinnamon and sprinkled with colored sugar. Easy to make and quite delicious.