Tender Caramelized Onions in Microwave

I used to think caramelized onions were this fancy cooking thing that took forever on the stove. My mom would spend what felt like hours stirring onions in a pan, and half the time they’d end up burned anyway.

Then I discovered you can make them in the microwave. It sounds weird, I know, but it actually works great. No constant stirring, no worrying about the heat being too high. You just pop them in, check on them every few minutes, and they come out sweet and golden. For busy weeknights when you want that rich onion flavor without all the fuss, this method is a game-changer.

What Kind of Onions Should I Use?

White onions are called for in this recipe, but you can easily swap them out for yellow or sweet onions if that’s what you have on hand. Yellow onions are actually the most popular choice for caramelizing since they have a nice balance of sweetness and sharpness that develops beautifully as they cook. Sweet onions like Vidalia or Walla Walla will give you an even sweeter result, while red onions will work too but might give your dish a slightly different color. The key is slicing them thin and evenly so they cook at the same rate in the microwave.

Options for Substitutions

This quick microwave method is pretty straightforward, but here are some swaps you can make:

• White onions: Yellow onions work just as well and are actually the most common choice for caramelizing. Sweet onions like Vidalia or Walla Walla will give you an even sweeter result. Red onions can work too, though they’ll add a slightly sharper flavor.
• Butter: You can substitute with olive oil or vegetable oil if you prefer, using about 2-3 tablespoons. The butter does add a nice rich flavor though, so keep that in mind.
• Baking soda: This ingredient is key to speeding up the caramelization process in the microwave, so I wouldn’t recommend skipping it. If you don’t have it, you’ll need to cook the onions much longer and they might not get that deep caramelized color.
• Fresh thyme: Since this is optional, you can easily swap it for other herbs like rosemary or oregano, or use about 1/4 teaspoon of dried thyme instead. You can also skip the herbs entirely if you want plain caramelized onions.

Watch Out for These Mistakes While Cooking

The biggest mistake people make with microwave caramelized onions is rushing the process by using too high a power setting, which can cause the onions to burn on the edges while staying raw in the center – stick to medium power (50-70%) and be patient with the timing.

Don’t skip the baking soda, as this small amount helps break down the onions faster and creates that beautiful golden color you’re looking for.

Make sure to stir the onions every 3-4 minutes during cooking to ensure even browning, and if they start looking dry, add a tablespoon of water to prevent burning.

The onions are ready when they’re deep golden brown and smell sweet – if they’re still pale yellow, they need more time in the microwave.

What to Serve With Caramelized Onions?

Caramelized onions are like the perfect sidekick that makes everything taste better! I love piling them on top of grilled burgers or steak for that sweet, savory flavor boost, or stirring them into scrambled eggs for a fancy breakfast. They’re also amazing on pizza with goat cheese and arugula, or mixed into pasta with some cream and parmesan. For something simple, just spread them on toasted bread with a little cheese for an easy appetizer that always impresses.

Storage Instructions

Refrigerate: Your caramelized onions will keep beautifully in the fridge for up to a week in an airtight container. I love making a big batch because they’re so handy to have around for topping burgers, stirring into pasta, or adding to omelets throughout the week.

Freeze: These onions freeze really well for up to 3 months! I like to portion them out in ice cube trays or small containers so I can grab just what I need. Once frozen, you can transfer them to freezer bags to save space.

Use: You can use the caramelized onions straight from the fridge, or if they’re frozen, just thaw them in the microwave for 30-60 seconds. They’re perfect for adding instant flavor to soups, sandwiches, or pizza without any extra prep time.

Preparation Time	5-10 minutes
Cooking Time	12-15 minutes
Total Time	17-25 minutes
Level of Difficulty	Easy

Estimated Nutrition

Estimated nutrition for the whole recipe (without optional ingredients):

• Calories: 250-300
• Protein: 3-5 g
• Fat: 24-28 g
• Carbohydrates: 10-14 g

Ingredients

• 1/2 tsp baking soda
• 1 sprig fresh thyme
• 3 tbsp butter (I like Kerrygold unsalted butter for this)
• 3 cups white onion (thinly sliced, about 1/8-inch thick)

Step 1: Prepare the Onions

• 3 cups white onion, thinly sliced

Peel and thinly slice the white onions to yield 3 cups.

Using a sharp knife or mandoline will help to achieve even, thin slices which are key for even caramelization.

I recommend taking your time with this step for the best result.

Step 2: Combine Ingredients in a Microwave-Safe Dish

• 3 cups white onion, thinly sliced (from Step 1)
• 1/2 tsp baking soda
• 3 tbsp butter
• 1 sprig thyme (optional)

Place the sliced onions into a deep, microwave-safe dish.

Add the baking soda, butter, and, if using, the thyme sprig.

Gently toss or mix to distribute the butter and baking soda evenly among the onion slices.

The baking soda helps speed up caramelization.

Step 3: Initial Microwave Caramelization

• Onion mixture from Step 2

Microwave the onion mixture uncovered on high for 10 to 11 minutes.

The onions should soften and start turning a medium golden brown.

Make sure to select the correct wattage for your microwave, typically using the standard ‘high’ setting.

Keep an eye on the onions in the last few minutes to prevent burning.

Step 4: Continue Caramelization and Finish

• Partially caramelized onions from Step 3

After the initial cook, stir the onions well to ensure even caramelization.

Microwave for an additional 2 to 4 minutes, or until the onions reach your preferred level of caramelization.

Bubbles may form as the liquid cooks down—this is normal.

Let the onions rest briefly to allow bubbling to subside.

Personally, I like to taste the onions at this stage and decide if they need a tiny extra zap for deeper flavor.

Step 5: Serve or Store the Caramelized Onions

Serve the caramelized onions warm as a topping or ingredient, or let them cool and store in an airtight container in the refrigerator for up to 5 days.

The rich flavor will deepen as they rest.