Tangy Yucatecan Grilled Pork with Roasted Onions and Fresh Garnishes

Name: Tangy Yucatecan Grilled Pork with Roasted Onions and Fresh Garnishes
Ingredients: 2medium white onions, unpeeled; 1 1/2pounds well-trimmed, thin-cut, boneless pork steaks, cut from the shoulder or leg OR 1 1/2 pounds thin-cut, boneless pork chops; 1/4 cup orange juice; 1/2cup lime juice; Salt and freshly ground black pepper for seasoning the meat and vegetables; 3cups thinly sliced cabbage; 1/3cup roughly chopped cilantro, plus a few sprigs for garnish; 1pound (2 medium-large round) ripe tomatoes, cored and sliced 1/4-inch thick; 1large avocado, peeled, pitted and sliced 1/4-inch thick