In a pot, add the water, washed red and navy beans and 1 tablespoon of salt. Bring the mixture to a boil. Reduce heat and simmer, stirring occasionally, until the beans are tender, but firm, about 45 minutes to an hour. Once done, remove from heat and rinse.
In a large salad bowl, mix beans, onions, parsley and rosemary until evenly mixed.
In a separate bowl, add vinegar and olive oil. Mix in sugar until dissolved. Add about 2 tsp salt and pepper.
Stir dressing into the salad. Cover. Refrigerate to let the flavors blend.