Preheat the oven to 375 degrees.
Cream butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each. Add milk and vanilla.
In a separate bowl, stir together flour, baking soda, salt, and cream of tartar, and then add into the creamed mixture. Add the chopped pecans.
Shape dough into 1-inch balls, roll in extra sugar, and flatten slightly. Set the cookies 2 inches apart on cookie sheet. Bake for 10 to 12 minutes.