Mix the dry ingredients in a bowl with the blueberries and lemon zest.
In a separate bowl, mix together the eggs, vanilla, buttermilk, and lemon juice.
Using a cheese grater, grate the butter into the dry ingredients. Note that it is best to use cold butter and keep the mixture cold to keep butter from melting.Use your fingers to toss the butter into the mixture.
Add the wet ingredients to the dry mixture. Use your hands or a spoon to lightly mix or fold to avoid crushing the fruit and overworking the dough. Note that the mixture should be somewhat shaggy with some remaining flour visible.
Turn the dough out to a floured working surface. Work the dough into a flat circle 1-inch thick. This may require flipping the dough and flouring your hands. Keep in mind to not overwork the dough, as it will warm up the butter and crush the fruit, resulting in tough/heavy scones.
Using a sharp knife, slice the dough into “pizza slices.” (I typically do 8 slices.)
With a brush, wash the top surfaces of the dough with beaten egg. Sprinkle with sugar.
Place scones onto a non-stick mat and into a 450° oven. Leave about 1 inch between the scones, as they will grow.
Bake for 7 minutes and then turn off the oven. Do not open the door. Leave scones in the oven for another 8-10 minutes. Scones will be golden brown when they are done.
Remove scones and place on a wire rack to cool. Serve warm.