Preheat the oven broiler to high. Place a large skillet over high heat.
Sprinkle a generous pinch each of oregano, salt, pepper and paprika on a large piece of parchment paper. Drizzle a little olive oil over the top. Add the butter to the pan with a little olive oil. Turn breast fillets on the paper and sear in the hot pan for 4-5 minutes until golden on both sides. Discard parchment paper and wash hands.
Wash the tomatoes, but be careful to keep them on the vine! Cut the lemon into quarters.
Place both in a large roasting pan. Add the meat and all the liquid from the pan. Drape everything nicely with kitchen tongs, then place the bacon on top of the chicken breasts. Return the pan to medium heat, toss the rosemary sprigs briefly in it, and place in the roasting pan. Place the pan under the broiler for a good 14 minutes.
This dish goes well with roast potato cubes with garlic and rosemary.
