Line a large baking sheet with a silicone mat or parchment paper. Set aside.
Using very cold butter, cut the butter into small cubes. Set in the freezer while you prepare the other ingredients.
Sift the dry ingredients together: 2 1/4 cup flour; 1/4 cup sugar; 1/4 tsp salt; 1/2 tsp cinnamon; 1 Tbsp baking powder. Set aside.
Whisk together the wet ingredients: 1 large egg; 1 tsp vanilla; 1/2 cup yogurt; 1/4 cup milk. Set aside.
Get the butter out of the freezer and add to the dry ingredients. Using the pastry cutter, cut the butter into the flour until the butter is the size of pea gravel.
Add the wet ingredients to the dry ingredients. Add the blueberries. Mix with a spatula until just combined. You will need to work the dough with your hands to form the dough ball. You may find that some of the flour needs to be worked into the dough. You can add a tiny bit of milk to the mixture to help work the flour in. By tiny I mean no more than a Tbsp. Start with a splash and see how that helps the flour get worked in. As you work the dough, the blueberries will add water to the dough, so be careful to not get the dough ball too wet and sticky. It will be a bit sticky and that is ok. If it does get too sticky, you can add a bit of flour to your hands and work that into the dough.
Once you have formed the dough ball, split it into two even halves and form into 5-6 inch discs. I find this easiest to do with my hands. I place one of the smaller dough balls onto the baking sheet and press down gently. The disc should be about 1 inch thick and 5-6 inches round. I use my bench scraper to measure the width of the discs as the bench scraper is 6 inches long.
Using the bench scraper, cut the discs into six triangles. Don't worry if they are not perfectly even. Place scones into the fridge while you heat up the oven.
Preheat the oven to 400 degrees. I like to clean up while I am waiting for the oven to preheat.
Brush the tops of the scones with milk and sprinkle a bit of course sugar on top. Place on the middle rack in the oven. Bake for 18-20 minutes. Scones should be lightly golden on the top and flaky in the middle.
Let scones cool for a bit before biting into one. There's nothing like a fresh, warm scone straight from the oven. You will want to wait until they are completely cooled before adding the glaze or it will just melt off.
To make the glaze, add 1 Tbsp lemon juice to 1/2 cup of powdered sugar and mix vigorously until combined. Drizzle over the cooled scones and let it set for a bit. It will firm up quickly. If you like more drizzle, just make a double batch.
Enjoy your fresh blueberry scones!