Healthy Slow Cooker Lasagna Soup (Reader Favorite!)

Ingredients

• 1 lb. 95% lean ground beef
• 1 onion, diced
• 6 garlic cloves, minced
• 28 oz. canned crushed tomatoes (ideally San Marzano)
• 16 oz. marinara sauce (no sugar added)
• 3 cups chicken broth
• 2 tsp. Italian seasoning
• 10 whole wheat lasagna noodles (or regular)
• 1 zucchini, chopped
• 6 oz. fresh spinach
• 1/2 cup Parmesan cheese
• Salt and pepper