Evenly butter the bread slices on 1 side, cut into triangles. You can leave the crusts on or remove.
To a large bowl add the milk, eggs, sugar, vanilla, nutmeg and lemon zest. Whisk to combine. Grease the bottom of a square 8 x 8-inch (20 x 20 cm) baking dish with butter.
Add a layer of bread slices to the bottom of the pan, slightly overlapping. Sprinkle half of the currants, sultanas or raisins. Add the rest of the bread slices and the currants, sultanas or raisins. Pour over the custard so the bread is evenly coated. Gently press the bread slices so they all make contact underneath with the custard. Leave at room temperature for 20 minutes so allow the bread to soak the custard.
Preheat the oven to 350°F/180°C.
Bake the pudding, uncovered in the center of the oven for 30-40 minutes until browned.
Remove from the oven and allow to rest for 10 minutes before serving to allow the custard to set.
Video
Notes
* You can leave the slices out overnight to dry or lightly toast without browning