Preheat the oven to180°C.
Mix the butter, garlic, dill and lemon zest in a small bowl. Season with salt and pepper.
Cut the lemons into thin slices.
Make several deep insertions in the meat, then push the spiced butter into them.
Lay the lemon slices in a roasting tin, then place the lamb on top.
Rub the lamb with the leftover butter (all over).
Cover the dish with foil, then bake for about 65-80 minutes, depending on how well-cooked you like your lamb. (Check the packaging for cooking time). Take the foil off 30 minutes before the end of the cooking time and pour in the wine or stock. Keep basting the meat.
Remove the lamb from the oven, transfer to a large plate, cover and let it rest for 15 minutes.
Meanwhile, make some gravy from the cooking jus.
Carve the lamb, and serve with your favourite side dishes and the gravy.