Combine yoghurt, tandoori paste and 1 tablespoon lemon juice in a large bowl. Add chicken, place plastic wrap directly onto marinade and refrigerate for about 4 hours.
Preheat grill to high.
Divide chicken among skewers, being careful not to overcrowd the skewers. Places skewers on a tray and grill for 3-4 minutes on each side, or until just cooked through. Watch carefully to avoid burning.
Mix remaining lemon juice, oil, cayenne and cumin in a large bowl and season to taste. Add onion and tomatoes and toss to coat. Just before serving add coriander.
Place 2 skewers on each plate with salad and serve with a lemon wedge.