Caramelized Onion Pasta with Chili Oil

The first time I made this, my kitchen smelled so incredible that my neighbor actually knocked on the door to ask what I was cooking. That caramelized onion sweetness mixing with the spicy chili oil aroma is something else entirely.

I served this at a tiny dinner party last winter and watched three people go completely silent after their first bites. Sometimes the simplest combinations hit the hardest.

Ingredients

• 12 oz pasta: Spaghetti or linguine catch the sauce beautifully, but whatever shape you love works perfectly here
• 2 tablespoons olive oil: Use a decent quality oil since the flavor really shines through the caramelization process
• 1 large yellow onion: Yellow onions develop the best sweet flavor when cooked down slowly and patiently
• 3 cloves garlic, minced: Fresh garlic makes all the difference, avoid the pre minced stuff for this recipe
• 3 tablespoons extra virgin olive oil: This forms the base of your chili oil, so choose something with good flavor
• 1 tablespoon red chili flakes: Start here and adjust up or down depending on your spice tolerance
• 1 teaspoon smoked paprika: The smoked variety adds this gorgeous depth that regular paprika just cannot match
• 1 small garlic clove, thinly sliced: Thin slices will infuse the oil without burning too quickly
• 1 teaspoon soy sauce: This secret ingredient adds umami that makes the chili oil taste finished and complex
• Parmesan cheese: Freshly grated makes a huge difference over the pre grated stuff
• Fresh basil or parsley: These bright herbs cut through the rich sweetness and heat

Instructions

Caramelize the onions low and slow:

Heat your olive oil in a large skillet over medium heat, add the sliced onions with a pinch of salt, and cook for 25 to 30 minutes while stirring occasionally until they turn this deep golden brown color that smells incredible

Add the garlic at the right moment:

Toss in the minced garlic during the last 5 minutes of onion cooking time, stirring constantly so it fragrances the onions without burning

Make your chili oil infusion:

Heat the extra virgin olive oil in a small saucepan, sauté the sliced garlic for 1 to 2 minutes until fragrant, then add chili flakes and paprika while stirring continuously for 2 to 3 minutes until everything becomes beautifully aromatic

Finish the chili oil:

Stir in the soy sauce and let it simmer for 2 minutes to meld all the flavors together, then remove from heat and set aside

Boil your pasta water properly:

Bring a large pot of generously salted water to a rolling boil and cook the pasta until perfectly al dente, remembering to reserve 1 cup of that starchy pasta water before draining

Bring everything together:

Toss the hot pasta directly with those gorgeous caramelized onions in the skillet, drizzle with your homemade chili oil, and add pasta water as needed to create a silky coating sauce

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My sister texted me at midnight the first time she tried this recipe demanding the exact proportions because she could not stop thinking about it.

Getting The Onions Right

Do not try to rush the caramelization process by turning up the heat because you will end up with burned onions instead of sweet ones. Low and slow gives you that deep flavor that makes this dish sing.

Balancing The Heat

If you are sensitive to spice, start with half the chili flakes and taste the oil before tossing it with your pasta. You can always add more heat but you cannot take it away once it is there.

Make It Your Own

This recipe takes beautifully to additions like roasted cherry tomatoes, sautéed mushrooms, or even some crispy pancetta if you eat meat. The base flavor profile works with so many variations.

• Add a splash of pasta water before the chili oil if you want a creamier texture
• Toast some pine nuts or walnuts for crunch on top
• A squeeze of lemon juice right before serving brightens everything up

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Hope this becomes one of those recipes you make when you want something simple but deeply satisfying.

Recipe FAQs

→ How do I get the onions perfectly caramelized?

Cook sliced onions over medium heat with olive oil and a pinch of salt for 25-30 minutes, stirring occasionally. Don't rush this step—the deep golden color and sweet flavor develop slowly as the onions break down and release their natural sugars.

→ Can I adjust the spice level?

Absolutely. Start with 1 tablespoon of chili flakes and taste the oil before tossing with pasta. Add more for extra heat or reduce to 1-2 teaspoons for a milder version. You can always serve extra chili flakes on the side.

→ What pasta shapes work best?

Long strands like spaghetti, linguine, or fettuccine coat beautifully with the oily sauce. Short shapes like penne or rigatoni also work well, catching the caramelized onion pieces and chili oil in their ridges and tubes.

→ How long does the chili oil keep?

The chili oil will keep in an airtight container in the refrigerator for up to 2 weeks. Bring it to room temperature before using, or warm gently in a small pan. The flavors actually deepen after a day or two.

→ Can I make this vegan?

Yes. Simply swap the Parmesan for a plant-based alternative or nutritional yeast, and the dish becomes completely vegan while maintaining all the savory, umami-rich flavors from the caramelized onions and chili oil.

→ Why add soy sauce to the chili oil?

Soy sauce adds a subtle umami depth that complements the sweetness of the onions and the heat of the chilies. It won't make the dish taste Asian-inspired—it just rounds out the flavors and adds a savory richness.