Line cookie sheet with parchment paper
In large bowl combine flour, sugar, baking powder, cream of tartar and salt.
With a pastry cutter, cut in cold butter until mixture resembles coarse crumbs
In separate, medium-sized bowl, whisk eggs until lightly beaten.
Whisk in milk, sour cream and vanilla.
Using a spatula, fold egg/milk mixture into flour mixture until just combined.
Transfer dough into well-floured surface and gently knead the dough by hand until mixture forms a ball (if dough is too sticky, sprinkle more flour on top and knead in).
Divide dough until 4 even sized pieces and mold each into 3-4" disk. Place on cookie sheet and transfer to refrigerator while oven preheats.
Preheat oven to 400F.
Once oven has preheated, remove scone disks from refrigerator. Cut each disk into 4 wedges and arrange on parchment paper lined cookie sheet.
Brush with milk, sprinkle with cinnamon and sugar and bake 20-25 minutes.
Allow scones to cool before eating.