Note: Zante currants are aka “dried currants”; if you decide to make the scones with fresh berries, instead, (raspberries, blueberries, or strawberries), start with about ½ pint berries; hull and coarsely chop the strawberries, but leave raspberries and blueberries whole; freeze the whole berries or berry pieces in a single layer on a small baking sheet, and then add them to the dough after you add the buttermilk; be careful not to mash the berries into the dough, or you will color it with their juice.
Preheat oven to 400°; butter a baking sheet.
Make the dough: in a small bowl, combine the currants with warm water to cover; set aside for about 10 minutes until the currants are plumped; drain well.
Sift the flour, baking powder, and baking soda in a big mixing bowl or into a large bowl of a stand mixer fitted with the paddle attachment.
Add the sugar and salt; and stir to mix with a wooden spoon.
Cut the butter into ½-inch cubes and scatter the cubes over the dry ingredients. If you are mixing by hand, use a pastry blender to cut the butter into the dry ingredients; if you are using the mixer, pulse on and off so that you don’t break down the butter too much.
You want to end up with a coarse mixture with pea-size lumps of butter visible.
Add the buttermilk all at once along with the lemon zest and currants; mix gently with a wooden spoon by hand or on low speed if using a mixer.
Continue to mix just until you have a dough that holds together; if the mixture seems dry, add a little more buttermilk; you still want to see some of the butter pieces at this point.
Dust your work surface with flour, and turn the dough out onto it.
Using your hands, pat the dough into a rectangle about 18 inches long, 5 inches wide, and 1 ½ inches thick.
Brush the top with melted butter and sprinkle with sugar.
Using a chef’s knife, cut the dough into 12 triangles; transfer the triangles to the prepared baking sheet.
Bake for 24-35 minutes, until the tops are lightly browned.