Onion jam is a condiment that features cooked onions as its main ingredient. It can be served with a wide variety of dishes, including breads, meats and cheeses. To make it, onions are paired with liquids and spices to prepare a savory or sweet spread similar to fruit jams or preserves. The natural sugar in onions helps to give this vegetable-based jam a layer of sweetness that can be enhanced with fruit juice, wine or added sugar.
The process is similar to making jam with fruits. To make jam with onions, one chooses the onions he wants to use for the recipe and cooks them with a mixture of herbs, spices and water or vinegar. The onions are then put in a jar or other container for storage until needed.
Onion jam recipes often use red, yellow or white onions. For sweet jams, one might choose Georgia's Vidalia onion, which is known as an exceptionally sweet variety. When this type is not readily available, adding sugar to white or yellow onions will allow one to replicate the flavor of a naturally sweet onion. The tiny pearl onion, a specialty variety, works in most recipes that call for white or yellow onions. Certain onion varieties, such as red onions, are good choices for savory onion jam or onion relish recipes.
To prepare an onion for use in making jam, it is necessary to remove the onion's outer peel and to trim the ends of the bulb. The next step is slicing or dicing the onion, depending on the recipe's directions. The most common method for cooking the onions requires placing the slices or pieces of onion in a skillet or frying pan coated with a good quality vegetable oil.
Making onion jam requires that one caramelize or extract the natural sugars in an onion by cooking it slowly over medium heat. While cooking the onions, one must stir them frequently to keep the sugar from burning. Common recipes for onion jam require a cooking time of 30 minutes or more to soften and caramelize the onions. When making large amounts of onion jam, one might need to cook the raw onions in several small batches to ensure even cooking.