Whisk dry ingredients (flour through salt) in a large bowl. Lightly toss blackberries into the dry ingredients to separate the pieces of fruit.
Mix the heavy cream and zest (if using) into the dry ingredients with a fork or wooden spoon just until the dry ingredients come together.
Gather the dough into a ball and knead lightly against the sides and bottom of the bowl about 5 times, turning and pressing any loose pieces into the dough each time until they adhere, and the bowl is fairly clean. Transfer the dough onto a parchment paper lined baking sheet, and pat the dough into an 8-inch round, about ¾-inch thick.
Cut the round into 8 wedges.
Brush the tops with 2 to 3 teaspoons cream, milk, or melted butter. And, sprinkle with turbinado sugar (sugar-in-the-raw) if desired (it makes a pretty presentation if you do this step).
Bake at 425° F until the tops are golden brown, about 19-22 minutes. Let cool on a rack or serve warm. Cut scones apart with a serrated knife.