Quinoa (pronounced keen-wah) is a gluten-free grain with especially high vitamin and protein content, but many people don't use it because they aren't familiar with it. Quinoa grain has a bitter coating called saponin that must be washed off before it is eaten.
The secret to cooking whole quinoa is to wash the quinoa really, really well (rinse until it stops foaming, then a little more). You can also accomplish this by soaking the grain for several hours, changing the water several times during the process.
Toasting the rinsed quinoa is a good way to bring out the nutty flavor before adding the water and cooking it. Heat it over medium-low heat in a frying pan until the kernels are dry and starting to turn golden-brown.
To cook whole quinoa, use 2 parts water or broth to 1 part quinoa and prepare just like rice. Bring it to a boil and then simmer it until the liquid is absorbed.
Quinoa flour does tend to have a bit of a bitter flavor, so I always use something with a strong flavor to offset the bitterness--white sugar won't do it. You need something like brown sugar, molasses or maple syrup. Those types of flavors work well with the quinoa flavor.
If it is excessively bitter, it is probably rancid. Smell it. If the smell is really sour/bitter, like fumes rising up off it, it is rancid.
These alternate flours like quinoa and amaranth get rancid easily, so you need to store them in a tightly-closed container in the refrigerator or freezer. If it is rancid and you bought it recently, you should be able to return/exchange it where you bought it.