Caramelized Onion Pasta Chilli Oil

This hearty caramelized onion pasta with chilli oil has become my go-to recipe when I want to impress dinner guests without spending hours in the kitchen. The sweet depth of slow-cooked onions paired with the punchy heat of homemade chilli oil creates a pasta dish that tastes deceptively complex for its minimal ingredient list.

I first made this pasta during a particularly cold winter evening when I had little more than onions and pasta in my kitchen. What started as a necessity has become one of my most requested dishes when friends come over. The way the onions slowly transform from sharp to sweet never fails to amaze me.

Ingredients

• For the Pasta: 12 oz pasta of your choice – the shape matters less than the quality, so opt for bronze die-cut pasta if available for better sauce adhesion
• Salt: for pasta water – always salt your water until it tastes like the sea for properly seasoned pasta

• For the Caramelized Onions: 2 large onions thinly sliced – yellow or sweet onions work best as they have higher sugar content for better caramelization
• Olive Oil: 2 tablespoons – use a good quality olive oil as it forms the base of your flavor
• Butter: 1 tablespoon – adds richness and helps prevent burning
• Sugar: 1 teaspoon – optional but helps speed up the caramelization process
• Salt and Pepper: freshly ground – pepper makes a noticeable difference

• For the Chilli Oil: 1/4 cup olive oil – use a fruity rather than bitter variety for best results
• Chili Flakes: 1 tablespoon – Korean gochugaru offers complex flavor but regular red pepper flakes work well too
• Garlic: 1 clove minced – fresh garlic provides aromatic depth that powdered cannot match
• Smoked Paprika: 1/2 teaspoon – adds a subtle smokiness that elevates the entire dish
• Salt: 1/2 teaspoon – flaky sea salt works beautifully here

• For Garnish: Fresh parsley chopped adds brightness and color contrast
• Grated Parmesan Cheese: adds savory depth and creamy texture
• Extra Chilli Oil: for those who prefer more heat

How To Make Caramelized Onion Pasta with Chilli Oil

Start the Caramelization:

Heat olive oil and butter in a wide skillet over medium-low heat until the butter melts completely. Add your thinly sliced onions ensuring they're spread in an even layer. Sprinkle with a pinch of salt and toss to coat every strand with the oil-butter mixture. This initial seasoning draws out moisture and begins the caramelization process.

Master the Slow Cook:

Reduce heat to low and let onions cook undisturbed for about 5 minutes. Then stir occasionally every 3-4 minutes allowing a fond to develop on the pan surface between stirs. This process will take 25-30 minutes total. Around the 15-minute mark add the optional teaspoon of sugar if using. The onions are ready when they've reduced significantly in volume and turned a rich amber-brown color.

Prepare the Chilli Oil:

While onions are caramelizing heat 1/4 cup olive oil in a small saucepan over medium-low heat. Add minced garlic and cook for 30 seconds until fragrant but not browned. Add chili flakes and reduce heat to low immediately to prevent burning. Let infuse for 1-2 minutes stirring occasionally. Add smoked paprika and salt then remove from heat allowing the residual warmth to continue infusing flavors.

Cook the Pasta:

Bring a large pot of water to a rolling boil. Add enough salt until it tastes properly seasoned about 1 tablespoon per 4 quarts. Add pasta and cook until al dente according to package instructions usually 8-10 minutes. Before draining reserve at least 1/2 cup of the starchy pasta water this is crucial for creating a silky sauce.

Create the Final Dish:

Return the caramelized onions to medium heat if they've cooled. Add drained pasta directly to the onion pan along with about 1/4 cup of reserved pasta water. Toss continuously allowing the starchy water to create a light sauce that coats every strand. If the mixture seems dry add more pasta water a tablespoon at a time.

Finish with Chilli Oil:

Drizzle about half the chilli oil over the pasta and toss to incorporate. Taste and add more as desired depending on your spice preference. The oil should provide a warming background heat rather than overwhelm the sweet onions.

Pin it

My absolute favorite part of this recipe is watching how dramatically the onions transform. The first time I made this for my sister she couldn't believe the sweet intense flavor came from simple onions. It's become our traditional "catching up" meal whenever she visits from out of town.

Make-Ahead Options

The beauty of this recipe lies in its components. You can caramelize the onions up to three days in advance and store them in an airtight container in the refrigerator. In fact, the flavor often deepens overnight as they rest. The chilli oil can be made weeks ahead and stored at room temperature in a dark place. When ready to serve, you'll only need to cook fresh pasta and assemble the dish, making it perfect for entertaining without the last-minute cooking stress.

Pin it

Perfect Pairings

This pasta strikes a beautiful balance between rich and spicy flavors, making it ideal to pair with lighter sides. A simple arugula salad dressed with lemon juice and olive oil provides a peppery freshness that contrasts the sweet onions perfectly. For wine, reach for a medium-bodied white with good acidity like a Vermentino or Pinot Grigio to cut through the richness, or a light-bodied red like Pinot Noir that won't overwhelm the dish's nuanced flavors.

The Art of Proper Caramelization

The secret to truly exceptional caramelized onions lies in patience and temperature control. Many recipes claim quick caramelization in 10-15 minutes, but authentic caramelization requires at least 25-30 minutes of slow cooking. Keep your heat consistently medium-low throughout the process. If you notice the onions starting to burn rather than brown, lower your heat immediately and add a tablespoon of water to the pan. This technique, called deglazing, releases the flavorful brown bits from the pan surface while preventing bitterness from burnt onions. The gradual transformation from sharp, pungent raw onion to meltingly sweet caramelized strands is a fundamental cooking process worth mastering for countless other dishes.

Frequently Asked Questions

→ How do I ensure the onions caramelize properly?

Cook the onions over medium-low heat and stir occasionally to avoid burning. Adding a pinch of sugar can help with the caramelization process.

→ Can I adjust the spice level in the chili oil?

Yes, you can reduce the chili flakes for a milder heat or increase them if you prefer a spicier kick.

→ What type of pasta works best for this dish?

Any pasta works, but spaghetti, fettuccine, or penne pair particularly well with the caramelized onions and chili oil.

→ Can I make this dish ahead of time?

You can prepare the caramelized onions and chili oil in advance. Store them separately in airtight containers and combine with freshly cooked pasta when ready to serve.

→ What can I use as a garnish aside from parsley or Parmesan?

You can try fresh basil, crushed red pepper for extra spice, or a drizzle of balsamic glaze for a tangy touch.