It started with too many herbs and not enough time to use them.
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A few years back I had a herb garden that was doing better than I expected, which sounds like a good problem until you're standing there looking at more rosemary and thyme than any one household could reasonably use before it turns. So I started drying things down and making herb salt, and once I was doing that it seemed obvious to do the same with garlic. And once I was doing that, onion was the next logical stop. The only difference between onion salt and onion powder is whether you add salt to the tray while it's dehydrating. I made both. Then I decided I'd rather control the salt myself and just keep the onion powder straight.
That was the beginning of a habit I haven't stopped.
The case for making your own is actually a couple of things stacked on top of each other. The most obvious is that you know what's in it. A lot of store-bought onion powders have additives and anti-caking agents, and even the ones labeled 100% onion powder leave you guessing about whether those onions were organic or what they were sprayed with. When I buy organic onions from the store or farmer at my local market, I've got a pretty good picture of what I'm putting in my food and what I'm not. That matters to me.
The second thing is waste. Most people throw away the onion pieces that don't make it into the recipe. The papery layers, the ends, the bits that get trimmed off. I throw mine onto a small baking tray that lives in my oven. My oven is gas, which means there's always just a little ambient warmth in there from the pilot light, and that slow gentle heat dries everything down over time without me doing anything at all. I just pull the tray out when I need the oven and put it back when I'm done. When the tray starts to fill up or I'm running low, I grind it. That's the whole system.
If you've got an electric oven, the warming setting works the same way. No warming setting? The lowest temperature your oven goes, with the door propped open just slightly with a wooden spoon to let the moisture escape. Either way, you're looking for pieces that are completely dry and snap when you bend them. If they bend without breaking, they need more time. You don't want any flexibility left in them before they go into the grinder.
When they're ready, I crumble the dried pieces up with my hands first to break them into smaller bits, then run them through my spice grinder. I don't grind for a super fine powder. I go until it's ground enough that it'll dissolve into whatever I'm cooking, with maybe a few slightly larger flakes in the mix. It takes less than five minutes from tray to container, including cleaning the grinder. And the same exact process works for garlic.
The container it goes into is a four-compartment condiment bar. It was designed to hold garnishes at a bar. I use it for the spices I reach for constantly while I'm cooking: garlic powder, onion powder, and whatever blend I'm going through at the time. Each compartment has its own little spoon and the whole thing sits right next to my stove. I flip the lid, grab what I need, and keep moving. I saw it and thought it would work perfectly for this, so I bought it. The fact that it was designed for lemon wedges and cocktail cherries is neither here nor there. A good tool is a good tool. The express purpose it was designed for has nothing to do with whether it'll work for what you need.
I go through it fast enough that I'm not worried about airtight storage. Typically refilling about once a month. If you're making larger batches or storing for longer, a mason jar in a cool dry place is the right call and it'll keep for several months that way. Once you've got the habit going though, you probably won't be storing it long enough for that to matter.
The garlic detail is worth repeating because it gets overlooked. Every bit of garlic skin and leftover garlic that would go in the trash goes on the same tray. Same process. Same grinder. You end up with two homemade spices from ingredients most people throw away, in about the same amount of time it would take to drive to the store. Not including parking.
From The Field: Before something hits the trash, ask if it's got one more job in it first.