Heat the oil in a soup pot. Add the leeks and saute over medium heat until translucent, about 5 minutes. Add the red pepper and garlic and saute the vegetables for another 5 to 8 minutes, or until the leeks turn golden and the pepper softens. Add the stock.

Drain the liquid from the canned tomatoes into the soup pot, then finely chop the tomatoes before adding to the soup. Bring to a rapid simmer, then lower the heat. Cover and simmer gently for 10 minutes.

Meanwhile, cook the orzo in a separate saucepan until al dente, then drain. Add the cooked orzo to the soup along with the spinach and herbs. Stir in the lemon juice, then add 1 to 2 cups of water, enough to give the soup a dense but not overly crowded consistency.

Season with salt and pepper, then simmer over very low heat until heated through. Serve.