Porchetta and Polenta

Name: Porchetta and Polenta
Ingredients: 3 pounds boneless pork shoulder, trimmed of excess fat; Kosher or sea salt; Grated zest of 1 lemon; 3 cloves garlic, chopped; 2 teaspoons fennel seeds, plus more for sprinkling; 16 fresh sage leaves, chopped; 2 teaspoons chopped fresh rosemary; Freshly ground pepper; Extra-virgin olive oil, for drizzling; 3/4 cup white vinegar; 3 tablespoons sugar; 1 bay leaf; 1/2 teaspoon fennel seeds; 1/4 teaspoon red pepper flakes; 1 large red onion, thinly sliced into rings; 1 tablespoon extra-virgin olive oil; 1 tube (about 18 ounces) prepared polenta, cut into 1/4-inch-thick rounds