Penne With Spinach and Feta

uncooked whole-wheat penne (or other small shaped pasta)

olive oil

medium onion, diced (about 1 cup)

garlic cloves, minced

pear or cherry tomatoes (about 1/2 pound) or 1/2 (14.5-ounce) can diced tomatoes, drained

fat-free, less-sodium chicken broth

fresh baby spinach or arugula leaves

salt

pepper

crumbled feta cheese