Build the Base

1. Warm olive oil in a large pot over medium heat. Add onion, carrot, and celery with a pinch of salt. Cook until softened and glossy, about 8 minutes.
2. Stir in garlic and cook for 30 seconds.
3. If desired, add a spoonful of tomato paste for deeper flavor and stir for 1 minute to caramelize.
4. Pour in tomatoes and scrape the bottom of the pot to prevent sticking.

Simmer and Finish

1. Add chicken, potatoes, broth, oregano, bay leaf, and red pepper flakes. If using, add the Parmesan rind. Bring to a gentle boil, then lower to a simmer.
2. Cover and cook for 25 to 35 minutes, until chicken is cooked through and potatoes are tender.
3. Remove chicken to a plate, shred with two forks, and return to the pot.
4. If using pasta, add it now and simmer until al dente. Adjust salt and pepper to taste.
5. Stir in lemon zest, a squeeze of lemon juice, and parsley before serving.
6. Let the soup sit for 5 minutes off the heat before serving. Taste and adjust lemon if needed.

Slow Cooker Method

1. Place onion, carrot, celery, garlic, potatoes, tomatoes, oregano, bay leaf, red pepper flakes, and broth into a slow cooker.
2. Nestle chicken on top. Cook on Low for 6 to 7 hours or High for 3 to 4 hours, until chicken shreds easily and potatoes are tender.
3. Remove chicken, shred, and return it to the slow cooker. Stir in lemon zest, juice, parsley, and salt to taste.
4. If using pasta, boil it separately and add it to bowls before serving.