In a large skillet over medium heat, combine the ground beef and onions. Cook, stirring frequently, until meat is no longer pink and onion is transparent, about 10 minutes. Remove from heat and drain fat. Season with allspice, salt, and pepper; set aside.
Heat the olive oil in a skillet over medium heat. Stir in the pine nuts to coat with oil. Continue stirring until the nuts turn golden brown, about 2 minutes. Set aside.
Assemble by spreading half of the hummus over the bottom of a 9x13 casserole dish. Tear the pita bread rounds into pieces and layer these over the hummus. Spoon the remaining hummus evenly over the bread, then top with pine nuts. Sprinkle with paprika, half the parsley, and drizzle with lemon juice. If adding a meat layer, top the casserole with ground beef mixture and remaining parsley, and serve.
