Preheat the oven to 350F
In a large bowl, beat the butter, sugar and zest until fluffy; beat in the egg. In a small bowl, stir together the flour, baking powder, baking soda and salt; add to the butter mixture in three additions, alternating with the juice in two. Add the cranberries along with the final addition of flour.
Pour into a buttered 8"x4" loaf pan and bake for an hour, or until springy to the touch.
Cool for a few minutes before turning out onto a wire rack.