Preheat oven to 375 degrees.
In a large bowl, sift together the flour, sugar, baking powder, salt, and lemon zest.
Add the cubed butter to the mixture. Using a pastry blender or your fingers, begin to blend the butter with the dry ingredients by breaking up the cubed butter. Continue to work it until the mixture looks like a coarse meal and the largest butter pieces are the size of peas.
Add in the fresh blueberries and mix them in with a fork.
In a small bowl, mix 1 cup of heavy cream and the egg with a fork until well combined.
With the same fork, make a well in the middle of your dry ingredients. Add in the cream and egg. Begin stirring the wet ingredients into the dry, working from the middle out toward the edges of the bowl until all of the flour is hydrated.
Pour the batter out onto a lightly floured surface and pat it together into a disk. Continue to pat the dough into an 8-inch circle of an even thickness, about 3/4 of an inch. Use a sharp knife to cut the disk into 8 even triangles. Gently place each triangle onto a cookie sheet lined with parchment paper.
Stick in the freezer for 15 minutes to get the butter cold.
Bake for 20 minutes or until the scones are golden brown.
To Make the Glaze: Whisk together the fresh lemon juice and powdered sugar. The glaze should be thin enough to drizzle, yet thick enough to sit on top of the scones. Allow the scones to cool slightly before drizzling the glaze generously over the scones. I like to go over each scone twice to make sure they have enough!