Add chopped onion and celery to a large pot or Dutch Oven with a lid. Cook uncovered over medium heat with olive oil, tomato paste, and salt for ten minutes, stirring occasionally.
1 large yellow onion, diced, 2 stalks celery, chopped, ¼ cup extra virgin olive oil, ¼ cup tomato paste, ¼ teaspoon salt
Add chopped seasonal vegetables and minced garlic and stir to coat. Cook for another 5 minutes uncovered.
2 cups seasonal vegetables*, chopped, 4 cloves garlic, minced
Add vegetable broth, bay leaves, and black pepper and stir to combine. Place cover on top, but off-center, leaving an inch of space for steam to escape. Simmer for 15 minutes.
5 cups vegetable broth, 2 bay leaves, ¼ teaspoon black pepper
Remove cover and stir. Add orzo and spinach and bring heat down to low. Cover and cook for 20 more minutes.
1 cup orzo, uncooked, 2 cups spinach
Remove bay leaves and taste orzo to make sure cooked al dente. Serve hot.