Marinate the lamb cutlets in the lemon juice and 4 tbsp olive oil for about 20 mins. Brush courgettes with another 2-3 tbsp olive oil and season.
Lift the lamb cutlets out of the marinade, season well and barbecue or griddle for 1-3 mins on each side. Barbecue or griddle the courgettes for 2-3 mins on each side until tender and charred. Barbecue or griddle the lemon slices for 30 secs-1 min each side to char and caramelise slightly.
Transfer the lamb and courgettes to a platter. Scatter on the mint, lemon zest, butter beans, chilli, spring onions, feta and seasoning, and gently toss. Drizzle with olive oil and add the barbecued lemons to the platter to squeeze over.