Preheat the oven to 350 degrees F. Grease a medium baking pan (9″ round). Line bottom of pan with parchment paper. Grease once again over the wax paper; dust with all- purpose flour.
Place beans and cinnamon stick in large saucepan. Cover beans with fresh water; bring to boil over high heat. Reduce heat to low and simmer for 30 minutes. Drain beans; place in large bowl, mash until smooth.
Combine milk, orange juice, orange zest, eggs, and butter in a blender. Process until smooth. Stir processed egg mixture and raisins into mashed garbanzo beans.
Sift the cornstarch and baking powder over garbanzo bean mixture. Stir to incorporate.
Pour batter into the prepared pan. Bake for 45-50 minutes, or until a toothpick inserted in center of cake comes out clean.
Allow cake to cool before inverting onto serving plate. Sprinkle with powdered sugar and remaining orange zest, and garnish with pomegranate seeds.