Heat 1 TBS broth in a 10-12 inch stainless steel pan or skillet. Healthy Sauté onion over medium heat for about 5 minutes in broth, until translucent. Add garlic and continue to sauté for another minute.
Add rest of broth, diced tomatoes, and lemon juice. Bring to a simmer on high heat. Once it starts to simmer reduce heat to medium and simmer for about 5 minutes.
Add herbs, olives, capers, and cod fillets; cover and simmer for about 5 minutes, depending on how thick the fish is. Season with salt and pepper to taste. Serve cod mixed with tomato herb sauce.