For the Meatballs:

• 8 ounces ground sausage, casings removed
• 8 ounces ground beef
• 1/2 cup breadcrumbs
• 1 large egg
• 1 teaspoon Italian seasoning
• 1/2 teaspoon garlic powder
• 1/2 teaspoon salt
• 1/2 teaspoon black pepper
• 1/4 cup grated Parmesan cheese
• 3 Tablespoons lukewarm water

For the Soup:

• 1/4 teaspoon crushed red pepper flakes
• 2 1/2 Tablespoons olive oil
• 1 large yellow onion, diced
• 4 large carrots, peeled and chopped
• 2 stalks celery, finely chopped
• 8 cloves garlic, minced
• 8 cups chicken broth
• 4 cups beef broth
• 2/3 cup acini di pepe pasta
• 4 cups fresh spinach, roughly chopped
• 1 teaspoon salt, more to taste
• 1/2 teaspoon black pepper, more to taste
• 2/3 cup Parmesan cheese
• 3 Tablespoons freshly squeezed lemon juice