Dice the carrots, celery & onion. Heat a large Dutch Oven over medium heat. When it is good & hot, add the olive oil.
Then add the carrots, celery, onion and the spices - Italian seasoning, salt, pepper and red pepper flakes.
Sauté for 4-5 minutes until the vegetables begin to soften. Add in the garlic & sauté for about another minute, until the garlic becomes fragrant.
Run your knife thru the spinach a couple times, chopping it into bite sized pieces. Add it to the soup pot.
Next add the pasta and give everything a good stir, scrape the bottom of the pot to loosen the brown bits. Pour in the tomatoes, stock and water.
Increase the heat to high and stir well to combine. Bring to a boil, then reduce the heat to medium - you'll still want to keep it a light bubble and cook until the orzo is cooked thru - about 8-9 minutes.
Continue to stir the soup often. The orzo has a tendency to stick to the bottom of the pan. In addition, stirring it will release the starches in the pasta and help to thicken the soup.
When the orzo is cooked, remove the soup from the heat. Add a squeeze of fresh lemon juice and about a tablespoon of chopped parsley for bright fresh flavor.
Notes
Substitute brown rice or quinoa for the orzo. Both are equally delicious! Just be sure to adjust the cooking time accordingly.