Preheat the oven to 200°C/gas mark 6. Make 2 double thickness squares of kitchen foil, large enough to wrap up each piece of fish, and put a salmon fillet in the middle of each.
Scatter over the mixed fresh herbs and halved tomatoes, then season with freshly ground black pepper and top with the butter and halved lemon slices. Scrunch up the foil to enclose the salmon fillets like a parcel, then put on a baking tray.
Bake in the oven for 12 minutes, then rest for 2-3 minutes before opening. If your salmon is still slightly undercooked, re-scrunch the foil parcels and put back in the oven for a further 2-3 minutes.
Take the salmon out of the parcels and serve with the tomatoes and juices spooned over the top.