Melt butter in a soup pot over medium heat. Add onions and carrots stirring occasionally, until the onions soften, about 5 to 8 minutes. Do not let the onions or carrots brown. Sprinkle a teaspoon of salt over the carrots and onions as they cook.
Add the stock, water, ginger and strips of orange zest. Cover and simmer until carrots soften, about 20 minutes.