In a bowl, add the cubed lamb, season with salt and pepper and mix thoroughly.
Thread the cubed lamb onto skewers, along with pieces of halloumi and onions. Add them in any order you like and transfer to a plate.
Place on a grill pan over high heat and let it get very hot. Drizzle with some olive oil and cook the lamb souvlaki for about 2 minutes on each side, until they brown nicely.
Transfer to an ovenproof baking dish or a baking pan and roast for 10-12 minutes.
When ready, serve the lamb souvlaki with your choice of green salad and tzatziki.