1
Heat milk in a medium saucepan over medium-low heat, stirring, until steaming, 4 to 6 minutes. Whisk eggs in a large bowl until blended; gradually whisk in 1/4 cup sugar. Slowly whisk in the hot milk until blended. Whisk in vanilla, lemon zest and nutmeg.
2
Add bread and raisins (or craisins) to the milk mixture; gently fold together. Press down lightly with the back of a large spoon. Cover and set aside at room temperature.
3
Butter the bottom and sides of a round 2-quart baking dish with 1 teaspoon butter. Preheat oven to 350 degrees F. Put a kettle of water on to boil.
4
Cut each pear half lengthwise into 4 slices. Place in a medium bowl and toss with lemon juice.
5
Heat a medium skillet over low heat until hot. Add the remaining 3 tablespoons butter and swirl until just melted and the foam subsides. Sprinkle the remaining sugar over the melted butter. Arrange the pear slices on their sides in the pan in an even layer. Increase the heat to medium-low and, without stirring, let the pears begin to brown and the sauce slowly caramelize, adjusting the heat as needed to prevent burning, about 10 minutes. Remove the pan from the heat and carefully turn each pear slice with a fork. Return to the heat and cook until the sauce is uniformly golden, 2 to 4 minutes more.
6
Carefully transfer the pears one at a time to the prepared baking dish, arranging them decoratively in a circle and slightly overlapping them if necessary. Use a heatproof silicone spatula to scrape any remaining syrup over the pears.
7
Set the baking dish in a shallow baking pan. Spoon the bread and custard mixture into the baking dish. Press down on the bread until it is submerged in the custard. Place the pan in the oven and carefully add the hot water to the shallow baking pan until it is halfway up the sides of the baking dish.
8
Bake until the pudding is browned on top and set in the center, 1 to 1 1/4 hours. Carefully remove the pan from the oven. Transfer the baking dish to a wire rack and let cool for at least 45 minutes. To serve, run a knife around the edge of the pudding. Place a serving platter over it and invert the pudding onto the platter.