1In a large soup pot, heat the butter. Add the onions and seasoned salt and cook over medium heat for 5 minutes. Add the clams and their liquid , the clam juice and the water. Bring to a boil, reduce the heat to medium low, and simmer, covered for 30 minutes.
2Add the potatoes, bring to boil, reduce heat and simmer until the potatoes are soft about 15 minutes. Stir in the tomato soup, tomato paste and cayenne, and simmer for 10 minutes.
Cool the chowder and refrigerate for several hours or overnight.
3Reheat gently. adjust the seasonings and add more water if the chowder is too thick, and serve.