Mix the beef, cumin, paprika, salt and plenty of freshly ground black pepper together in a bowl. Divide the mince mixture into 8 portions and press each portion firmly onto flat skewers, each one around 10–12cm/4–4½in long.
Place a non-stick griddle pan over a high heat and brush with a little oil. Cook the kebabs for about 10 minutes, turning 3–4 times, or until well browned on the outside and thoroughly cooked on the inside – there should be no pink remaining.
Add the onion wedges to the griddle for the last 5 minutes of the cooking time and griddle until lightly charred, turning occasionally.
To make the dip, mix the yogurt with the preserved lemon and garlic. Spoon into a serving dish, drizzle with olive oil and sprinkle with a little paprika.
Put the onions onto a serving plate and top with the kebabs, scatter with fresh mint and sprinkle with a little more paprika. Serve with the dip.