In a food processor, combine onion, tomato, capsicum, parsley, garlic, green chilli pepper, 7 spice, salt, black pepper and cardamom in a food processor; pulse to form a loose paste. In a large bowl, combine the mixture with the minced beef, and knead the ingredients with your hands. Shape the meat mixture into elongated meatballs.
In a medium bowl, lightly season the potatoes with salt and pepper and gently coat them with a couple of tablespoons of vegetable oil.
Arrange the meatballs and potatoes on a large baking sheet. Roast in the oven for about 20 minutes, until the potatoes have browned (the potatoes will not have cooked through.)
In a medium bowl, add the tahini, yoghurt, water, lemon juice, paprika, salt and black pepper; whisk the ingredient together until it has a smooth consistency. Taste and adjust seasoning as necessary.
Remove the roasting pan from the oven. With a tong, transfer and alternatively arrange the kofta meatballs and potatoes into a large cast iron skillet or casserole dish. Pour the tahini sauce over the meat and potatoes, and make sure it is evenly distributed and fully covers everything. Roast in the oven for an additional 35 minutes. Remove from oven and allow to rest for about 15 minutes.
Toast the pine nuts in a small pan until golden brown on medium-low heat. Garnish the kofta bil tahini with the toasted pine nuts and chopped parsley. Serve and enjoy!