Put the minced lamb, ground spices, garlic, mint, lemon rind and 1 tablespoon of the lemon juice from the cucumber salad in a large bowl. Season generously with salt and pepper, then mix all the ingredients together until well combined. Mould the spiced mince into 8 slightly flattened sausage shapes, then thread 2 sausages each on to 4 long metal skewers. Set aside.
Meanwhile, to make the cucumber salad, mix together the cucumber, pepper, parsley, mint and tomatoes in a bowl. Season generously with salt and pepper, then stir in the remaining lemon juice. Set aside.
Place the lamb skewers on a grill rack, then slide under a preheated grill for 6–7 minutes, turning once, until cooked through and browned all over.
Arrange the salad on to serving plates, then place the lamb skewers on the salad. Sprinkle over the sumac, if using, and serve with griddled pitta bread and lemon wedges, if liked.