Add the cumin seeds, coriander seeds, carom seeds, and black peppercorns to a dry sauté pan. Toast the spices over medium heat, shaking the pan gently in a circular motion, until they become fragrant.
Once toasted, transfer the spices to a grinder and blend until powdered.
Next, prepare your vegetable mix. Place the red onion, tomato, garlic, ginger, and deseeded green chili in a food processor or vegetable chopper. Pulse the ingredients until they're finely chopped.
In a large mixing bowl, combine the ground beef, salt, 1 tbsp of the prepared spice mix, the finely chopped vegetable mix, and bone marrow. Mix everything together until well combined.
Divide the mixture into even portions and shape each one into a flat patty.
Heat beef tallow in a large cast-iron pan over medium heat. Once the tallow is hot, add the beef kababs and fry them in batches until they're all cooked. Each patty should take around 4-5 minutes but can vary depending on the thickness.
Serve your Pakistani Chapli Kababs hot, and enjoy!