1. In a large saucepan, combine the milk, sugar, rice, and salt. Cook, uncovered, for about 2 hours, over very high heat, stirring occasionally and scraping the sides of the saucepan with a spatula.
2. Five minutes before the rice is cooked, lightly beat the egg yolks in a bowl. Mix them with a little warm rice to warm them up, then add them to the pudding mixture. Stir well and cook for 5 more minutes. Remove from heat, let cool slightly, then stir in the maple extract and orange zest. Divide the preparation into 6 ramekins that can go in the oven. Refrigerate.
3. At least 2 hours before serving, preheat the broiler and place a rack in the highest position in the oven. Place the ramekins on a baking sheet. Cover each with 1/8 inch of sugar, spreading it evenly to cover the surface perfectly. If the layer is not even, the sugar will burn in some areas before caramelizing in others. Place the baking sheet under the broiler and monitor constantly. The sugar will quickly boil, melt, and caramelize. When the sugar has a dark caramel color over the entire surface, remove the baking sheet and refrigerate the puddings. Serve chilled.