Caramelizing onions is a technique that involves slowly cooking down onions at low heat to draw out their natural sugars and obtain a sweet, sticky, intensely flavored result. Caramelized onions are a versatile ingredient that can add tons of flavor to dishes like soups, sauces, burgers, pizza, sandwiches, and more. While the traditional method is to caramelize onions on the stovetop, using the microwave can speed up the process considerably.
What is caramelization?
When onions are heated, the moisture evaporates, concentrating the natural sugars. When the sugars reach a high enough concentration and temperature, they start to brown, reacting with amino acids through the Maillard reaction. This reaction produces that characteristic sweet and rich “caramelized” flavor.
Caramelization is different from simply cooking or softening onions. It requires certain conditions to occur:
- Low, gradual heat – The sugars need time to concentrate as the moisture slowly evaporates.
- Dry environment – Extra moisture will inhibit caramelization.
- High heat towards the end – Heat above 329°F is needed to initiate the Maillard browning reactions.
These conditions can be challenging to achieve in a microwave, but not impossible.
Challenges of microwaving onions
Microwaves heat food differently than conventional methods. While microwaves can generate high temperatures, the heat is uneven and inconsistent for several reasons:
- Microwaves penetrate and heat foods from the inside out, rather than outside in.
- Heating occurs rapidly but unevenly, with hot spots based on the food’s composition.
- Moisture content impacts what areas heat up most.
These microwave characteristics make it difficult to caramelize onions:
- The rapid, uneven heating doesn’t allow time for slow caramelization.
- Excess moisture is present from the onions releasing liquid.
- The edges may burn while the centers remain undercooked.
However, with the right techniques, these challenges can be addressed.
How to caramelize onions in the microwave
Here is a step-by-step guide to successfully caramelizing onions in the microwave:
- Slice the onions thinly. Thin slices maximize surface area, allowing moisture to evaporate quickly.
- Arrange slices on a microwave-safe dish. A broad dish instead of a pile promotes even cooking.
- Cook onions in short 1-2 minute bursts. Check and stir frequently to prevent overcooking edges.
- Remove excess moisture. Dab cooked onions with paper towels. Discard any released liquid.
- Repeat cooking in short bursts. Onions will shrink as moisture evaporates.
- Sprinkle a bit of sugar once onions start to brown. The sugar aids caramelization.
- Finish with high heat. Cook for the last 1-2 minutes on high power to achieve browned caramelized edges.
The most important tips are slicing thinly, cooking in short intervals, and removing excess moisture during the process. This helps concentrate the onion sugars and achieve that caramelized sweetness.
Microwave caramelized onion tips
- Sweet onions like Vidalias work best since they have more natural sugars.
- If edges start to burn, cover them with small pieces of aluminum foil.
- Add a splash of oil to help conduct heat if onions seem unevenly cooked.
- Scrape up any browned sticky bits that develop in the dish and incorporate.
- The total cooking time will depend on the amount of onions, but expect 15-30 minutes.
Pros and cons of microwaved caramelized onions
Microwaving produces slightly different results from traditional stovetop caramelization. Here are some pros and cons:
Pros:
- Much faster cooking time. Caramelized onions can be ready in under 30 minutes instead of 1-2 hours.
- Less oil/butter needed since there is no sautéing.
- Don’t have to stir constantly like on the stovetop.
- Minimal effort – just need to check and stir every couple minutes.
Cons:
- Can be tricky to perfect. Takes some trial and error.
- Onions come out softer, less browned than stovetop method.
- Flavor is good but doesn’t develop as deep/complex notes.
- Not as versatile. Works best for recipes where onions are mixed in, not stand-alone side dish.
For maximum caramelized flavor and browned texture, stovetop is still ideal. But microwaved onions can be a handy shortcut when you’re short on time.
Dishes to use microwaved caramelized onions
Here are some of the best uses for onions caramelized in the microwave:
Sandwiches and burgers
Mix into any sandwich fillings, spreads, or burger toppings. The soft texture and mild sweetness pair perfectly.
Salads and sides
Toss microwaved onions into grain bowls, pasta salads, or as a topping for cooked vegetables. Will add a hint of richness.
Soups and stews
Stir in microwaved onions to boost savory brothy dishes. The softness will blend right in.
Casseroles and bakes
Fold into dishes like lasagna, mac and cheese, egg bakes, enchiladas, etc. The onion flavor will permeate throughout.
Pizza
Microwaved onions are great sprinkled on homemade or frozen pizzas. Adds sweetness to counter the savory toppings.
Omelets and scrambles
Mix in onions to make fluffy omelets or scrambles extra flavorful.
Dips and spreads
Stir caramelized onions into dips, cheese balls, creamy spreads, etc. Pairs perfectly with crackers and chips.
Onion Caramelization Time Comparison
Here is a table comparing the time it takes to caramelize 1 pound of sliced onions using different methods:
| Method | Time |
|---|---|
| Stovetop | 45-90 minutes |
| Slow cooker | 4-6 hours |
| Pressure cooker | 15-20 minutes |
| Microwave | 15-30 minutes |
As you can see, the microwave is significantly faster than conventional stovetop caramelization, almost as fast as a pressure cooker!
Storing and freezing caramelized onions
Storage
Properly stored, caramelized onions will last:
- Room temperature – 3-4 days
- Refrigerated – Up to 1 week
- Frozen – Up to 3 months
Store them in an airtight container in the fridge or freezer. The browned sugars will harden when cold. Reheat gently before using.
Freezing
Microwaved caramelized onions freeze exceptionally well:
- Spread cooked onions in a single layer on a sheet pan or plate. Freeze until hard.
- Transfer to freezer bags or containers, removing as much air as possible.
- Freeze for up to 3 months.
- Thaw in the refrigerator before using.
Frozen onions will soften when reheated or incorporated into hot dishes. Freeze in recipe-sized portions for easy use later.
Conclusion
Caramelizing onions in the microwave produces perfectly serviceable results, ideal for mixing into a variety of savory dishes. While the texture may not be as browned and the flavor as complex as stovetop methods, microwave onions can be ready in just 15-30 minutes. With a bit of technique, microwaving is a fast, low-effort shortcut for weeknight cooking.