Rub the salt, pepper and garlic powder all over the lamb, rubbing it into the meat. Heat 1 Tbsp. oil until hot but not smoking in a large oven-safe pan or roasting pan.
If the drippings are burnt, pour off all of them, wipe out the pan & heat another Tbsp. of oil until hot. Add the onions and smashed garlic cloves, season with salt & pepper, & sauté until golden.