Mario Batali's Arista alla Porchetta | La Cucina Grandinetti

Ingredients

• One 4-pound boneless pork loin roast, butterflied (have the butcher do this)
• Salt and freshly ground black pepper
• 1/2 cup extra-virgin olive oil
• 1 medium onion, thinly sliced
• 1 fennel bulb, trimmed, fronds reserved and chopped, bulb thinly sliced
• 2 pounds ground pork shoulder
• 2 tablespoons fennel seeds
• 2 tablespoons chopped fresh rosemary
• 6 cloves garlic, thinly sliced
• 1 cup fresh bread crumbs
• 2 large eggs, lightly beaten
• 4 red onions, cut in half
• 1 lemon, halved