Place egg whites in a small bowl; let stand at room temperature for 30 minutes.
Meanwhile, in a small bowl, cover raisins with boiling water. Let stand for 5 minutes; drain and set aside. In a large saucepan, cover rice with water; bring to a boil. Drain the liquid; add milk to rice. Bring to a boil. Reduce heat; cover and simmer for 15-20 minutes or until rice is tender; set aside.
In a large bowl, cream butter and sugar until light and fluffy. Beat in egg yolks. Add the rice mixture, raisins and orange zest. Beat egg whites until stiff; fold into batter. Spoon into a greased 10-in. tube pan. Sprinkle with crumbs.
Bake at 350° for 55-60 minutes or until a toothpick inserted in the center comes out clean. Immediately invert pan; cool completely, about 1 hour.
Run a knife around side and center tube of pan. Remove cake to a serving plate. Dust with confectioners' sugar. Serve warm or chilled.