Heat a large nonstick skillet over medium heat. Coat pan with cooking spray. Add yellow onion to pan; cook 4 minutes, stirring occasionally. Add green onions, rice, and nuts; cook 2 minutes, stirring frequently. Stir in 1/2 cup water and next 6 ingredients (through pepper); bring to a boil. Cover, reduce heat, and simmer 8 minutes or until liquid is absorbed. Remove from heat; cool. Stir in lamb.
Rinse grape leaves with cold water; drain well. Pat dry with paper towels. Remove stems; discard.
Spoon 1 tablespoon rice mixture onto center of each grape leaf. Bring 2 opposite points of leaf to center; fold over filling. Beginning at 1 short side, roll up leaf tightly, jelly-roll fashion. Place stuffed grape leaves, seam sides down, in a vegetable steamer. Steam 1 hour and 30 minutes.