Add 1 Tbl. olive oil, onion, celery and carrots to Dutch oven and sauté over medium-high heat for 5-6 minutes until tender or choose a low and slow method and sauté them over medium-low heat, covered for 15 minutes. Add in garlic and stir another minute. Stir in broth, lemon juice, 2 tsp. lemon zest, 1 tsp. fresh rosemary (or 1/2 tsp. dried), oregano, salt & pepper. Bring to a boil, stirring occasionally. Add tortellini and reserved meatballs. Reduce heat to medium; simmer, stirring occasionally, 8-10 minutes or until pasta is tender. Just before serving add the fresh spinach leaves.