A good substitute for vegetable broth is the cooking or steaming liquid from vegetables–not as rich and flavorful, perhaps, but it works.
2/3 c vegetable broth
1/2 c fresh minced cilantro
1/2 c minced onion
1/2 c finely chopped red bell pepper
1/4 c white or white wine vinegar
1/4 c extra virgin olive oil
1 t salt
1 t fresh oregano leaves, minced, or 1/4 t dried oregano
1/2 – 1 t crushed red pepper flakes
1/2 tsp black pepper
4 medium garlic cloves, minced
1. Whisk together all ingredients in a bowl. Allow to sit for a little while, if you can, to allow flavors to meld.