1. Make the prune filling: Combine prunes, raisins, brandy, light-brown sugar, zest, and 1/4 cup water in a small saucepan over medium-low heat. Bring to a simmer and cook, stirring occasionally, until syrupy, about 10 minutes. Remove from heat and transfer to the bowl of a food processor; process until smooth. Transfer to a small bowl; cover and refrigerate.

2. Make the rice filling: Bring 1 1/2 cups water and salt to a boil in a medium saucepan. Add rice, cover, and reduce heat to medium-low. Cook, stirring occasionally, until rice is tender and water has evaporated, about 20 minutes. Stir in milk, sugar, vanilla, cinnamon, and nutmeg. Simmer, stirring frequently, until rice is very tender, about 30 minutes. Remove from heat.

3. Whisk together eggs until well incorporated in a medium bowl. While whisking constantly, add a small ladle of hot milk mixture to the eggs. Repeat process until half of the milk mixture has been incorporated. Then slowly return egg mixture to pot while continuing to whisk. Return pot to the heat and cook, stirring, until thickened, 2 to 3 minutes. Remove from heat and transfer to a medium bowl. Let cool for 30 minutes, stirring occasionally. Press plastic wrap directly on the surface of the rice mixture. Refrigerate for at least 30 minutes.

4. Make the crust: Combine warm water and yeast in a small bowl. Let stand until foamy, about 5 minutes. Whisk together flour and salt. In the bowl of an electric mixer fitted with the paddle attachment, beat together the eggs and vanilla until pale yellow and tripled in volume. Add sugar and butter and beat until thoroughly combined. Using a rubber spatula, stir in yeast mixture until just incorporated; stir in flour mixture. Turn out dough onto a generously floured work surface and sprinkle with more flour. Gently knead for about 1 minute. Transfer to a large bowl coated with softened butter. Cover with plastic wrap and set aside in a warm place until doubled in bulk, about 1 hour.

5. Preheat oven to 350 degrees with rack in center of oven. Punch down dough and remove from bowl. Pat dough into a 13-inch round and place in a 9-inch pie plate. Spread bottom evenly with prune filling. Stir rice mixture to loosen and add to pie plate. Bake on a parchment-lined baking sheet until crust is golden and center is set, about 1 hour. If crust browns too quickly, tent with a piece of foil that has a hole in the center. Let cool on a wire rack for 15 minutes, then chill in refrigerator until completely cooled, at least 2 hours and up to overnight. Serve at room temperature.