Heat oil in a large nonstick skillet over medium heat. Add bell peppers, onion, and next 5 ingredients (onion through cumin); saute 5 minutes or until tender. Add juice; cook 8 minutes or until reduced to 2 1/2 cups.
Combine black beans and half of tomato juice mixture in a bowl; stir well. Stir cannellini beans into remaining tomato juice mixture. Set both aside.
Preheat oven to 325°.
Combine cheeses in a bowl; toss well. Line a 9-inch pie plate with foil, allowing 6 inches of foil to extend over opposite edges of pie plate. Repeat procedure with another sheet of foil, extending foil over remaining edges of pie plate. Coat foil with cooking spray; place 1 tortilla in bottom of dish. Spread 1 cup cannellini bean mixture over tortilla; sprinkle with 1/4 cup cheeses. Place 1 tortilla over cheeses, pressing gently. Spread 1 cup black bean mixture over tortilla; sprinkle with 1/4 cup cheeses. Place 1 tortilla over cheeses, pressing gently. Repeat layers, ending with the remaining black bean mixture and cheeses.
Bring edges of foil to center, and fold to seal. Bake at 325° for 40 minutes. Remove from oven; let stand, covered, 10 minutes. Remove foil packet from dish. Unwrap pie, and slide onto serving plate using spatula. Cut into wedges, and garnish with cilantro, if desired.