Preheat oven to 425. Line a baking sheet with parchment paper.
In a mixing bowl, add the flour, sugar, salt, baking powder, and cream of tartar, stirring to combine. In a smaller bowl, stir together the yogurt and milk. Add the yogurt to the flour mixture and stir gently until it all comes together and a soft dough forms, being careful not to overwork the dough.
Turn the dough out onto a floured surface and pat it lightly into a circle, about 1-inch thick. Using a biscuit cutter, cut rounds of the dough and place them onto a prepared baking sheet. Repeat until all the dough has been used.
Bake about 13-15 minutes or until cooked through and golden. Serve immediately, while hot. Great with butter and jam or honey, with gravy, or as the bread for a breakfast sandwich, etc.