Lemony Tortellini Soup

Bahan-bahan (4 porsi)

• 1 tablespoon olive oil
• 1 white or yellow onion, diced
• 1 fennel bulb, diced
• 2 medium carrots, sliced
• 2 celery stalks, sliced
• 5 cloves garlic, minced
• ½ teaspoon crushed red pepper flakes
• 8 cups chicken stock
• 16 ounces fresh tortellini
• 2 large handfuls fresh baby spinach
• 1 lemon, zest and juice (about 2 tablespoons juice)
• 2 to 4 tablespoons fresh dill (or other fresh herbs), to taste
• fine sea salt and freshly-ground black pepper
• freshly-grated Parmesan cheese