Preheat the oven to 400F and cover a baking sheet in greased parchment paper.
Mix the flour, sugar, baking powder, baking soda, and salt in a medium sized bowl.
Grate the butter into the bowl and stir loosely with a fork.
Add in yoghurt, egg, vanilla, and lemon zest. Mash with hands until a loose dough forms.
Mash the blackberries into the dough, being careful not to overwork it.
Flatten dough onto parchment paper into a roughly 12" circle, 1" thick. Slice like pizza into 8 slices.
Arrange the slices on the baking sheet and top each evenly with 1/2 teaspoon of sugar.
Bake for 15 minutes and enjoy.
To prep ahead of time: place the butter in the freezer, premeasure the dry ingredients in a plastic bag, and premeasure the wet ingredients in a plastic bag. Keep the wet ingredients in the refrigerator until ready to use.