How to Caramelise Onions: 3 Different Methods
Whether you’ve got 5 minutes or 20, there’s a method that’ll work. Here are four ways to caramelise onions, from super quick to hands-off oven methods. Pick what suits your evening and get cooking.
Quick Pan Method: How To Caramelise Onions In 10 Minutes
This is the easiest way to get caramelised onions on the table fast for taco night or a laid-back sharing spread.
- Slice your onions: Peel and slice the onions pole-to-pole (from root to tip) into thin slices. Thinner slices cook faster.
- Heat the pan: Add a drizzle of oil to a wide frying pan and warm over a medium-high heat. A wide pan gives more surface area, so the onions brown more quickly.
- Add onions and a pinch of salt: Toss to coat in the oil. Salt helps draw out moisture and speeds up softening.
- Boost the browning: Once the onions start to soften (after a couple of minutes), add:
- a small pinch of sugar (optional, but speeds up caramelisation)
- a splash of water if the pan looks dry, to stop catching / sticking.
- Stir often: Cook for 7-8 minutes or until done, stirring regularly. Adjust the heat if they’re browning too quickly – you want deep golden, not burnt.
- Finish: Once done your onions should be clearly caramelised, sweet to taste and soft.
Use white onions for a slightly sharper, savoury edge in your fajitas, and red onions when you want sweeter, jammy flavour on tacos and nachos. If you slice your onions extra-thinly you may be able to caramelise them even quicker.
Make sure to keep an eye on your onions while cooking, as the time required will vary based on thickness.
How To Caramelise Onions In The Oven
Have you ever wondered if it’s possible to caramelise onions in the oven? The answer is yes! It’s great when you want hands-off cooking while prepping your fillings and sides.
- Preheat the oven: Preheat your oven to medium-high.
- Slice and season: Toss sliced onions with oil, salt, and a small pinch of sugar in a roasting tin, then spread them out evenly.
- Roast and stir: Roast for 45–60 minutes, stirring every so often (about every 10 minutes) to stop them burning at the edges. If they look dry, add a splash of water.
- Cook until golden: Once deep golden and soft, remove from the oven.
Oven caramelised onions are brilliant when you’re already roasting peppers or other veggies for Mexican-inspired trays and sharing platters. Be sure to check on them regularly to ensure they are cooking well.
Grill Method: Charred & Caramelised Onions
If you’re after a smoky BBQ flavour, try caramelising your onions under the grill. This way you can add an extra layer of depth and those crispy bits everyone loves.
- Preheat the grill. Set to a medium-high heat.
- Prepare the onions. Toss sliced onions with oil and salt, then spread them on a grill-safe tray.
- Grill and turn. Place under the grill and cook for 45-60 minutes, turning and stirring every so often. Look for soft onions with crispy, caramelised edges and a sweet, smoky flavour.
- Finish and serve. Add a squeeze of lime or a drizzle of your favourite salsa to brighten them up.
Red onions work especially well here. They’re naturally sweeter and develop a beautiful, deep colour under the grill.
