2 cups all-purpose flour
1 tsp. baking soda
1 tsp. cream of tartar
¼ tsp. salt
6 tbsp. sugar
6 tbsp. cold unsalted butter, cut into small pieces
½ cup whole milk or heavy cream
1½ tsp. vanilla extract
For the topping:
¼ cup sugar
1½ tsp. ground cinnamon
Preheat the oven to 400° F. Line a baking sheet with parchment paper or a silicone baking mat. In a large mixing bowl combine the flour, baking soda, cream of tartar, salt and sugar; stir together with a fork. Add the cold butter to the flour mixture and cut the butter into the dry ingredients using a pastry cutter or two knives, until the mixture is crumbly and the largest butter pieces are the size of peas.
Combine the milk and vanilla in a measuring cup. Pour the liquid over the dry ingredients and stir together with a fork just until the mixture forms a cohesive dough. If necessary, knead the mixture just a few times by hand to bring the dough together. Transfer the dough to the prepared baking sheet and form a large round disc about 8-9 inches in diameter. In a small bowl, whisk together the sugar and cinnamon for the topping. Sprinkle generously over the top of the dough round (you will not need to use all of the topping.)
Bake for about 15-18 minutes, or until a toothpick inserted in the center comes out clean. Allow to cool on the pan, then slice into 6-8 wedges for serving.