Preheat oven to 400 degrees F. Line a large, rimmed baking sheet with parchment paper and set aside. 

In a large bowl, combine the flour, sugar, baking powder, baking soda, salt and mix well. Stir in the lemon zest. 

Cut the butter into the flour mixture using a pastry cutter or 2 knives until the butter is in pieces the size of large peas.

In a large liquid measuring cup mix together the buttermilk, lemon juice, and vanilla and then pour it over the flour/butter mixture. Stir together a few times. Then knead with your hands just 2-3 times until the dough starts to come together. Be careful not to over-knead or the scones will be tough instead of flaky.

Turn the dough out onto a surface dusted with 1-2 tablespoons flour. Form the dough into a round and divide it in thirds. 

Working quickly, gently pat each dough piece out into a circle 5 to 6 inches in diameter and then divide the circle into 6 pie-shaped wedges. Place the scones on the prepared baking sheet and repeat this step with remaining dough pieces until you have 18 small scones.

Brush scones with melted butter and sprinkle with a little bit of granulated sugar (if desired). Bake in preheated 400 degree F oven for 15 minutes or until lightly golden brown and cooked through. Serve warm or cooled.