Slice the onions in half and remove the peeling and film. Slice or dice your onion, depending on your preferences. Sliced onions work well for making onion powder, while chopped onions are great for adding to soups and stews and work the same as onion flakes.

If your dehydrator does not have fine mesh screens, line the trays with parchment paper or silicone dehydrator liners.

Place the sliced or chopped onion in a single, even layer on each of the dehydrator sheets. Ensure that there is ample room for the air to flow around each tray.

Set the dehydrator to 125ºF (52ºC) and place each of the filled trays into the dehydrator.

Dry for 10-24 hours, or until all of the pieces are brittle and break easily. Humid environments will take longer than dryer environments, so using the break test is the most reliable.

Turn off the dehydrator and allow the sliced or minced onions to completely cool in the dehydrator, or remove the trays to the open air to cool for approximately 1 hour.

Once the onions are completely cooled to room temperature, transfer them to a glass jar with a lid for conditioning - this checks for excess moisture.

Place the glass jar in a visible location for 24 hours, shaking it a few times throughout. Do not place it in direct sunlight, as the heat can cause a greenhouse effect that will cause moisture to build in the jar.

If any condensation or fogging shows in the jar, return your food to the dehydrator and dry again until it is brittle and passes the conditioning test.

If your food passes the conditioning test, transfer it to airtight jars or containers (or mylar bags) for storage. Store for 4-12 months, discarding if there are any signs of spoilage.

For onion powder: Add the completely dried onion slices (or flaked onion) to a spice or coffee grinder reserved for the purpose of grinding spices and powders. Grind until it is broken down into a fine powder. Then transfer to an airtight jar or container to store for 2-6 months.