Preheat oven to 350 degrees F. In a medium saucepan, melt butter over medium-high heat. Add 1/2 cup of the onions, the celery, and apple; saute for 5 minutes. Stir in rice, seasoning packet from rice mix, 3/4 cup of the broth, and garlic. Bring to a boil. Cover and simmer for 10 minutes or until liquid is absorbed. Rice should be al dente. Transfer to a medium bowl; stir in pecans. Set aside.
Place 12 to 15 large cabbage leaves in a large bowl. Cover with boiling water; let stand for 2 to 3 minutes or until wilted. Cut off thickest part of each cabbage leaf. Place 2 tablespoons of the rice mixture near the stem end of a leaf. Fold over sides and roll up. Do not roll too tightly as the rice will expand as it cooks. Repeat with remaining leaves and rice mixture.
Place cabbage rolls, seam sides down, in a shallow baking dish. Pour marinara sauce over the top and sprinkle with remaining onions. Cover pan tightly with aluminum foil. Bake in preheated oven for 1 hour. Serve hot with sauce.