Pakistani Meatballs with Gravy (Koftay)

In a medium bowl, mix lean ground beef, half of the onions, chili powder, black pepper, cloves, cumin and cardamom. Shape the mixture into approximately six 2 inch meatballs. In a large, heavy saucepan over medium heat, cook and stir the remaining onion in the vegetable oil until tender. Mix in the yogurt, lentils, ginger paste, garlic paste, coriander seed, water, red pepper and salt. Place the meatballs into the mixture. Reduce heat to low and cook 30 minutes, until meatballs are evenly browned and lentils are tender.