Dreamy baked onions you can prepare with minimal effort. A side dish both homey and elegant to grace your table on holidays, festive family gatherings and even weeknights.
- Continue reading for tips on how to bake onions for best results, including recipe variations (3 min read)
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One of our favorite ways to slow roast onions is with dark aged balsamic and nutty, sweet brown ale to balance the complex acidity of the vinegar with its malty, caramely flavors.
The resulting glorious partnership between the flavorful liquid base which infuses the onions as heat transforms them into soft, caramelized goodness is one we like to capture again and again. It is also proof of what seems to us a fundamental principle in cooking, especially within the realm of cooking with beer.
Onions and dark beer, along with butter and thyme create a powerful, harmonious combination.
Ingredients for Baked Onions
This recipe is very simple and virtually impossible to get wrong. You will need:
- onions – see below for notes on suitable varieties
- olive oil – about a tablespoon, but you can be more generous
- butter – about 1/2 tbsp sliver gets placed onto each of the halved onions to help them brown
- balsamic vinegar – use well-aged variety with depth of flavor and lower acidity
- dark ale – with low or non-detectable bitterness and pronounced caramely, roasty sweetness (less hoppy brown ales and porters make the best candidates, you can also use a lager such as bock or doppelbock)
- brown sugar – optional, use up to 1/4 cup only if the beer you procured is not sweet enough; for this post we used a brown ale sweetened with maple syrup so we omitted the brown sugar altogether
- thyme, salt and pepper – thyme is THE herb that goes best with slowly cooked onions, especially when dark ale and balsamic join the party
- baking dish/onion baker – you do not need a special onion baker inspired dish, anything oven safe and a bit deeper (about 3 inches) and appropriately sized will do.
What Type of Onions to Use?
For best results choose a mild or sweet onion type and try to select ones that are similar in size so that they can bake evenly. We recommend the following higher-sugar content varieties:
- sweet Vidalia onions
- sweet Maui onions
- white onions
- red onions
- yellow onions
We usually buy the onions that look the freshest and are in best shape since quality and appearance are key to the taste and presentation of this dish, especially if you’ll be serving it to guests.
Here is a Guide to Onions you might find useful.
How to Bake Onions (Step by Step)
Slow roasting onions (i.e. baking them) turns them into an appetizing, flavorful vegetable side few can refuse.
The prep work is minimal and the cooking largely hands off, except for occasional basting. What you do need a bit more of is patience.
Let the onions cook for as long as they need to in order to soften and caramelize amidst the delicious liquids.
NOTE: While you can roast the onions (we suggest oven temperature of 425 F) if you are short on time, baking them as we instruct in the recipe will give you better results. Think more tender, juicier and sweeter onions petals. Plus, you will get to enjoy the aromas wafting out of the oven longer.
Turn your oven on to 350 F or 375 F, depending on how strong it is and start by cutting the onions in half, lengthwise. Peel the outer paper layer and the top most layer immediately underneath it. Rinse the peeled halves. (#1 and #2 above).
Arrange the onion halves face up into a baking dish. (Do not be concerned if space is a bit tight initially – during baking they will shrink in size and fit better.) Drizzle with a bit of olive oil and then balsamic vinegar. (#3 and #4 above).
Pour the dark ale around the onion halves, place a thin piece of butter onto each half and season with salt and pepper. Add as much thyme as you’d like. You can also place a few sprigs right into the balsamic/beer liquid.
Bake at 375 F for about an hour, possibly a bit longer. Start basting the onions occasionally after 30 minutes have passed.
When Are the Baked Onions Done?
The exact time will depend on the type, size and number of onions you are slow roasting as well as your desired doneness.
For softer, more caramelized onions allow a bit longer. If you see them browning too much for your liking and the pan juices begin to dry out you can add a couple of tablespoons of water and loosely tent the baking dish with aluminum foil.
How to Serve Baked Onions
Serve the onions as soon as you pull them out of the oven if you can, they do smell irresistible. Garnish with fresh thyme if you’d like and some fresh ground pepper and a few sea salt flakes are always a nice touch.
Drizzle a bit of the juices over or around each onion if plating individual servings or provide an appropriate spoon for guests to be able to do the same if serving family or buffet style.
Baked Onions Recipe Variations
- apple cider – substitute apple cider vinegar and apple juice or apple cider for the balsamic and dark ale
- red wine – substitute red wine vinegar and a hearty, sweeter red wine for the balsamic and dark ale
- stock (beef, vegetable, chicken) – use stock instead of ale
- amp up the herbs – use more thyme and add rosemary, garlic and other herbs you like
- cheese – sprinkle some cheese (grated Parmesan or Pecorino, slice of Swiss or Gruyere) just before you take the onions out of the oven
- stuffed baked onion halves – brown some ground beef with spices while the onions are cooking. About 3o mins in take them out and scoop out the top few petals of each half. Place the semi-hollowed onions back in the oven. Dice the top layers as soon as you can touch them, mix them with the browned ground beef. Take the onions out of the oven again, scoop the beef mixture over them and bake until desired doneness.
- 4 large onions (such as Vidalia, white, yellow or red)
- 1 tbsp olive oil
- 1/3 cup aged balsamic vinegar
- 12 oz sweet dark ale or lager (brown ale or porter, bock or doppelbock)
- 1 tbsp brown sugar (optional, in the event that the beer has bitter notes)
- 4 tbsp butter, slice in 1/2 tbsp slivers while still cold
- thyme (to taste, but at least 4 sprigs fresh plus more for garnish or 1/2 tbsp dried thyme leaves)
- 1 tsp salt and 1/2 pepper, adjust to taste
- Turn the oven on to 375 F. * Halve the onions lengthwise and peel away the paper layer and the outermost layer immediately underneath it. Rinse the onion halves.
- Arrange the rinsed halves face up inside a baking dish. If they do not fit perfectly, do not worry, they will get smaller while slow roasting. Drizzle the olive oil and then the balsamic over them.
- Pour the dark beer around the onions and place a sliver of butter on top of each onion. Season with salt and pepper, then thyme.
- Bake at 375 F for about half an hour, then pull them out and baste with the juices from the baking dish. You can baste a couple of more times until they are done. Cook for at least 1 hour total time, longer if you'd like softer, sweeter onions. TIP: If the onions begin to brown more than you'd like and the pan juices dry out excessively, add a few tablespoons of water and cover the dish with aluminum foil.
*Each oven is calibrated differently so if you know yours to be quite strong, consider 350 F.
SHORTEN THE TIME If you don't have much time you could roast the onions at 425 F to speed up the process. We recommend slow roasting them at the lower temperature though.
MAKE AHEAD Even though baked onions are best served right out of the oven, you can make them ahead. Cook them the day before, let them cool off a bit, cover and keep refrigerated. Reheat in 375 F oven for about 10 minutes. Be sure to spoon over some of the pan liquids over the onions before you take them out of the oven.