Mix the peanut butter and sugar in a bowl. In another bowl, mix the egg, vanilla extract, baking powder, and cinnamon together. Combine the two mixtures and stir until you have a thick cookie dough. This dough will look a little greasier and smoother than standard cookie dough.

Roll the dough into balls and place them on a baking sheet lined with parchment paper, leaving enough space between them. Use a fork to flatten the balls slightly, making a diamond pattern in the dough.

Leave the cookies to cool completely on the baking sheet.