Melting Spanakopita Cabbage

Name: Melting Spanakopita Cabbage
Ingredients: 1 small head green cabbage ( 2¼ pounds ), outermost leaves removed; 4 tablespoons extra-virgin olive oil , divided; ½ teaspoon salt , divided; ½ teaspoon ground pepper , divided; 1 cup thinly sliced yellow onion; 2 ounces reduced-fat cream cheese (about ¼ cup ), softened; 1½ tablespoons minced garlic (from 5 medium cloves ); ¾ teaspoon dried oregano; ¼ teaspoon ground nutmeg; 2½ cups reduced-sodium vegetable broth; 2 teaspoons cornstarch; 2 teaspoons water; 4 cups baby spinach , chopped; ½ cup crumbled feta; 2 tablespoons chopped fresh dill , plus more for garnish; ½ teaspoon grated lemon zest (from 1 small lemon )