RECIPES:
Feb 20, 2023

How to Make Caramelized Onions

Prep Time: 5 minutes
Cook Time: 45 minutes
This “technique recipe” focuses on tips and tricks for making the best caramelized onions as a flavorful and versatile building block for other recipes.
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Caramelized onions are made by slowly cooking onions over a low heat to evaporate the water and draw out the sugars in the onions. They may not look the most appealing with their deep, uniformly brown color but they have a delicious mellow and sweet yet rich onion flavor and soft texture. They are not the same as grilled onions or charred onions cooked over high heat which will give you a bitter flavor. I use a mix of yellow onion and red onion in this recipe for a mix of mellow and sweet, as well as deeper onion flavor. 

Use these caramelized onions as the base for French onion soup, or as a flavorful addition to your favorite breakfast sandwich. I’ve included photos for visual cues to help you know when onions are at various stages as well as a how to video below. 

How to Make Caramelized Onions 

onions for caramelized onions

What Happens When Onions Caramelize? 

  1. Caramelization – When sugars are introduced to heat they break down and reform resulting in a sweet nutty flavor and brown color. 
  2. Maillard reaction – This is the name for the many small and complex chemical reactions that occur between amino acids and sugars when foods are browned, producing new flavors and aromas. Think caramelized onions but also like seared steak or even coffee. 

Key Ingredients in This Recipe 

  • Red onion – Red onions (actually purple in color) are frequently used raw because they have a fairly mild flavor. They’re less sweet than yellow onions. 
  • Yellow onion – Yellow onions are a great onion for general cooking because of their strong onion flavor. They also have a high sugar content which makes them great for caramelizing. 
  • Olive oil – While many people opt to make caramelized onions in just butter, I like using a combination of oil and butter since the oil has a higher smoke point. 
  • Butter – I use unsalted butter in this recipe. Because it contains milk solids, it helps the browning process more quickly than using just oil while also adding flavor. 
chopped onions for caramelized onions

Steps to Make Caramelized Onions

heating the butter
Step 1: Heat fat. 

Heat a large stainless steel or cast iron pan over medium heat. Add the olive oil to the pan and heat through, then add the butter and allow to melt.

Step 2: Sauté onions.

Working in batches, add the onions and toss quickly to remove the moisture from the onions. Sauté, stirring occasionally, until the onions are soft and start to brown.

saute onions for caramelized onions
cook onions
Step 3: Continue to cook. 

Sprinkle the sugar and salt over the onions, stirring to combine. Reduce the heat to medium-low and cook, stirring occasionally, until the onions are light brown and begin to caramelize, about 20 minutes.

Step 4: Cook until uniformly browned.

Continue to cook, stirring frequently, until the onions are uniformly brown and caramelized, about an additional 10 minutes. Remove the pan from heat. Let the caramelized onions cool and use or store until ready to use.

brown onions

Tips and Tricks for This Recipe 

Swaps and substitutions 
  • Any mix of yellow, red or Spanish onions or shallots can be used to make caramelized onions. I prefer the flavor of a mix but one or another can be used. 
  • While I like using a mix of olive oil and butter, you can try cooking the onions in bacon fat for a unique flavor. 
  • The onions can be chopped rather than sliced. 
Add More Flavor 
  • Deglaze the pan – Deglazing the pan with water, wine or stock helps remove the onions from the pan easily and adds more flavor. It helps to loosen any small bits stuck on the pan.
  • Vinegar – Try adding a bit of balsamic vinegar at the end of the cooking process to enhance the natural sweetness of the onions. 
  • Herbs – Adding herbs like thyme complement caramelized onions well (hello French onion soup). 
Tips for the Best Caramelized Onions 
  1. Don’t overcrowd your pan. Adding too many onions in the pan at once will steam them and produce water. I add the onions to the pan in batches.
  2. Patience! Caramelizing onions takes patience. The whole process takes about 45 minutes. Don’t try to rush the process by turning up the heat, think of them as a labor of love. 
  3. Low heat. Cooking the onions slowly over a low heat and occasionally giving them a stir helps to dry out the sugars and caramelize them without burning them. 
  4. A bit of sugar. I add a bit of sugar and salt to season the onions. The sugar also helps the onions to caramelize. 
How to Store Caramelized Onions 

If not using caramelized onions right away, add them to a resealable container. Store them refrigerated for up to a week or freeze for up to 3 months. I like to freeze them in ice cube trays for easy portioned out use.

How to Make Caramelized Onions

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Prep Time 5 minutes
Cook Time 45 minutes
Serves 1 cup

Ingredients:

  • 2 tablespoons extra-virgin olive oil
  • 2 tablespoons unsalted butter
  • 1 medium red onion, thinly sliced
  • 1 medium yellow onion, thinly sliced
  • 1 teaspoon granulated sugar
  • ½ teaspoon kosher salt

Instructions:

  • Heat a large stainless steel or cast iron pan over medium heat. Add the olive oil to the pan and heat through, then add the butter and allow to melt.
  • Working in batches, add the onions and toss quickly to remove the moisture from the onions. Sauté, stirring occasionally, until the onions are soft and start to brown.
  • Sprinkle the sugar and salt over the onions, stirring to combine. Reduce the heat to medium-low and cook, stirring occasionally, until the onions are light brown and begin to caramelize, about 20 minutes.
  • Continue to cook, stirring frequently, until the onions are uniformly brown and caramelized, about an additional 10 minutes. Remove the pan from heat. Let the caramelized onions cool and use or store until ready to use.

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