Cream the butter and sugar until light and fluffy. Then beat in the egg and vanilla extract.
Sift in the dry ingredients and mix together until everything is just incorporated. It's important not to over mix so you don't develop the gluten in the flour which makes for a tougher cookie.
Mix the sugar and cinnamon together in a bowl. Roll the dough into walnut sized balls between the palms of your hands, then roll in the cinnamon sugar.
Place on lined baking trays with enough space between each one to allow for spreading. Press the balls flat with the bottom of a glass or cup.
Bake for 8-10 minutes when the cookies should just be just staring to turn golden. Leave on the trays for a couple of minutes, then move to a wire rack to cool. Or just eat them whilst they're warm.
Notes
You can substitute 2 tsp of baking powder for the cream of tarter and bicarbonate of soda mix if you need to.If you like a crisper cookie, bake for two to three minutes longer.