Melt a tablespoon of real butter in a cup of milk. It isn't a perfect substitution, but it should work reasonably well.
Clarification:
Adding butter to milk as a substitue for buttermilk will not work. Contrary to its name, buttermilk has no butter in it; it is actually very low in fat. The best subtitution for buttermilk is a teaspoon of lemon juice or vinegar to each cup of milk. Since buttermilk has a higher acid content than "sweet milk", the addition of an acid will result in a substitution extremely close to that of buttermilk.
Simply add the lemon juice or vinegar and stir, then let stand a few minutes for the milk to "curdle", and it will look, taste and work pretty much the same as commercial buttermilk.
It can be done, but it's not the best. The texture will be different, and the taste will be extremely off.
salt
Doubtful this would work. Much different ingredient. Oil works well, Canola or Olive is the best for your health.
Use 1/10 of each ingredient in the recipe. While this is mathematically feasible, it is not always feasible to reduce a recipe to that degree. It might be best to fix the entire recipe and share it with friends or freeze some.
I believe that it depends upon the ingerdient. Something as small as brown sugar won't make much of a difference in size but the taste of the cookie will change. Your best bet is to use a substitute ingredient or go to your neighbors and ask for whatever it is that you are missing.
For baking purposes, you can substitute 1 cup of whole or 2% milk + about 2 teaspoons of vinegar (cider or white) for every cup of buttermilk called for in the recipe. It works best if the milk is not icy cold. Add the vinegar but don't stir. In a few minutes it will have clotted and is ready to pour in the batter.
Possibly, but it is always best just to use the ingredients that the recipe calls for.
it is best to bake in the high rack!
The best place to find a healthy seafood salad recipe would be to look into cookbooks for healthy cooking. Healthy cookbooks can teach you how to substitute ingredients for healthier ones.
Ground up nuts (e.g almonds, hazelnuts) can be used to substitute up to 1/4 of the flour quantity. However there is nothing which will completely substitute wheatflour, since it has a very unique set of properties which make it good for baking. If for some reason you cannot use flour, it is best to find a flour-free recipe rather than try to adapt a recipe to be flour-free.
Keep in mind that some people might not like it quite as much without the butter. But a pretty good substitute recipe can be found at http://thebloomingplatter.blogspot.com/2009/07/vegan-pound-cake.html
A book containing recipes and other information about the preparation ~ N.B It also may include important information about how to cook things and what's best to cook with. Some cookbooks do have substitution options (aka if you don't have a certain ingredient you can replace it with a different ingredient to continue making the dish) I still like the first answer though! *__*