My favorite is to butterfly it, soak it in a bottle of red wine, some chopped carrots, onions, garlic and some fresh herbs with some olive oil over the top. I will try to get a 24 hour marinade.
Then bring to room temp and grill over hot fire. When seared, move to an oven and bake until med rare.
So simple.
I've eaten a lot of lamb in my years and this is still the best way, I think.
