Mix in 2 more cups broth and simmer over low heat until absorbed, stirring occasionally. Add 2 more cups broth and simmer until barley is tender and creamy but still slightly firm to bite, stirring frequently and adding more broth if mixture is dry, about 35 minutes. If it is dry, add another 1/2 cup of broth and place the asparagus on top, cover and steam asparagus for 8 – 10 minutes or until crisp-tender.
Add tomatoes; stir in gently until heated through, about 3 minutes.
Mix in cheese, arugula and lemon peel. Season with salt and pepper. Serve