Heat oven to 375 degrees F. Combine flour, cream of tartar, soda, nutmeg and salt.

In a large bowl, use an electric mixer at med-low speed to cream the butter and 3/4 cup sugar until light and fluffy. Beat in the egg and vanilla.

Reduce mixer speed to low, and beat flour mixture in to the butter and sugar until well blended. Note: Add a little at a time as you might not need all of the flour.

Combine cinnamon and remaining 1/3 cup sugar. Note:There is enough of this cinnamon sugar to coat 3 batches of snickerdoodles, so save it for your next batches.

Pour the cinnamon sugar into a dish. Roll the dough into balls, then drop into the cinnamon sugar. Use a spoon to heavily coat the cookie dough balls, shake off the excess, then place on your baking sheet about 2" apart.

Bake until lightly browned and cracked on top, about 10 minutes.