Bring milk to a boil in a large saucepan over medium-high heat. Stir in rice, cinnamon, salt, and vanilla bean. Reduce heat to medium-low; cook, stirring occasionally with a wooden spoon, until rice is very tender and has absorbed all liquid, about 30 minutes.
Remove pan from heat. Stir in 3/4 cup granulated sugar. Cover; let cool, stirring occasionally. Discard vanilla bean.
Preheat oven to 350 degrees. Butter and flour an 8-inch springform pan. In a large bowl, combine the rice mixture, ricotta, whole eggs and egg yolks, and remaining 1/2 cup sugar. Pour into prepared pan. Bake until golden on top and almost set in the center, 65 to 70 minutes; cover with foil if starting to brown too much. Transfer pan to a cooling rack.
When cake has completely cooled, run a knife around edge to loosen. Gently
remove ring; transfer cake to a serving platter. Sprinkle with confectioners' sugar, and serve with sauce.