Preheat the oven to 375 degrees.
In a bowl add flour, sugar, baking powder, baking soda, lemon zest, and salt, cut the butter into the mixture with a pastry blender until you have fine crumbs.
Add the currants to it.
Add just enough buttermilk, until the dough leaves the side of the bowl. Place in a lightly flour surface and knead for 2 minutes, shape in to a round loaf. Place in a baking sheet cover with parchment paper and cut an X shape, brush with butter and bake until golden brown.