Mediterranean Green and White Beans

1 large onion, sliced thin
2 lbs green beans 
1 15 oz can white beans- no salt added, drained and rinsed
1 28 oz can whole peeled tomatoes
1/4 cup olive oil 
4 cloves minced garlic
2 Tbsp, tomato paste
1/2 cup chopped fresh parsley leaves
1 Tbsp chopped fresh dill (or 2 tsp. dried dill)
3/4 tsp salt
1/2 tsp black pepper
1/2 cup plain Green yogurt (low-fat)

In a large pot, heat oil over medium heat. Add the onion and saute until onion is softened, about 8 minutes. Add garlic and stir for 1 minute.  Stir in the tomato paste and cook until it's caramelized. (no more than a minute). 

Crush the tomatoes by hand over the pot and add with the juices. Add 1/2 cup of water to the mixture and bring to a boil. Add green beans, parsley, salt, pepper and dill and cover. Reduce heat to low and simmer for 30 minutes. Add the white beans and continue cooking covered until the green beans are tender. (about 30 minutes longer). Serve with a spoonful of yogurt on the top.