Caramelized Onion Chili Pasta

This hearty caramelized onion pasta with chilli oil has become my signature dish for dinner parties and quiet nights in alike. The sweet depth of slow-cooked onions meets the punchy warmth of homemade chilli oil, creating a pasta that's both comforting and exciting with every bite.

I first made this pasta when entertaining friends who love bold flavors but have varying spice tolerances. The genius of serving the chilli oil separately meant everyone could adjust their own heat level, and I've never looked back since.

Ingredients

For the Pasta

• 12 oz pasta of your choice: I prefer long strands like spaghetti or fettuccine that catch the oil beautifully
• Salt for boiling water: Always salt pasta water until it tastes like the sea for proper flavor development

For the Caramelized Onions

• 2 large onions: Sweet varieties like Vidalia work wonderfully here but any yellow onion transforms with slow cooking
• 2 tablespoons olive oil: Use a good quality one since it contributes significantly to the final flavor
• 1 tablespoon butter: Adds richness and helps the onions caramelize more evenly than oil alone
• 1 teaspoon sugar: Optional but helps accelerate the caramelization process if you're short on time
• Salt and pepper: Essential for drawing moisture out and developing depth of flavor

For the Chilli Oil

• 1/4 cup olive oil: Extra virgin works best as its flavor stands up to the chilli
• 1 tablespoon chilli flakes: Adjust based on your heat preference look for bright red flakes for best color and flavor
• 1 garlic clove: Choose fresh firm cloves without any green sprouts for clean flavor
• 1/2 teaspoon smoked paprika: Adds wonderful depth and smokiness without additional heat
• 1/2 teaspoon salt: Balances the heat and helps flavors meld together

For Garnish

• Fresh parsley: Brightens the dish visually and adds a fresh counterpoint to the rich flavors
• Grated Parmesan cheese: The salty tanginess works beautifully with the sweet onions
• Extra chilli oil: For those who want an additional kick

Step-by-Step Instructions

Caramelize The Onions

Step:

Heat olive oil and butter in a large skillet over medium low heat until butter melts completely. Add the thinly sliced onions with a pinch of salt and stir to coat evenly in the fat. The salt helps draw out moisture allowing better caramelization. Let the onions cook slowly stirring every 5 minutes for 25 to 30 minutes until they transform from white to golden to a deep amber brown. About halfway through add the optional teaspoon of sugar to help develop that beautiful caramelized flavor. The onions should reduce dramatically in volume and become jammy in texture. Be patient here as rushing this step will result in fried rather than caramelized onions.

Create The Chilli Oil

Step:

Pour olive oil into a small saucepan and warm over medium low heat until shimmering but not smoking. Add minced garlic and cook for 30 seconds until fragrant but not browned. Add chilli flakes and watch carefully as they begin to sizzle in the oil infusing it with their heat and color. Allow to bubble gently for about 1 minute then stir in the smoked paprika and salt. Remove from heat immediately to prevent the garlic from burning which would create bitterness. Let the oil steep while you prepare the pasta this allows the flavors to develop further.

Cook The Pasta

Step:

Bring a large pot of water to a rolling boil and add enough salt that it tastes like seawater approximately 1 tablespoon per quart. Add pasta and cook according to package directions until al dente typically 8 to 10 minutes. Before draining reserve about half a cup of the starchy pasta cooking water which will help create a silky sauce. Drain pasta but do not rinse as the starch coating helps the sauce adhere better.

Combine Everything

Step:

Return the skillet with caramelized onions to medium heat. Add the drained pasta directly to the onions and toss thoroughly to distribute the onions throughout. Add splashes of reserved pasta water as needed to create a light sauce that coats each strand. The starchy water helps emulsify the butter and oil with the pasta creating a silky consistency. Drizzle about three quarters of the chilli oil over the pasta and toss again ensuring even distribution.

Serve And Garnish

Step:

Divide pasta among warmed plates or bowls. Sprinkle with freshly chopped parsley for color and brightness. Offer grated Parmesan at the table for those who enjoy its salty richness. Place the remaining chilli oil in a small dish with a spoon so diners can add more heat according to their preference. Serve immediately while hot.

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The first time I served this pasta to my Italian neighbor she asked for the recipe which I consider the highest compliment possible. She particularly loved how the sweet onions balanced the heat from the chilli oil creating a perfect harmony of flavors that felt both familiar and exciting.

Storage And Reheating

This pasta stores beautifully in airtight containers in the refrigerator for up to three days. The flavors actually develop and improve overnight as the spices infuse throughout the dish. When reheating add a splash of water or olive oil to loosen the sauce and warm gently in a skillet over medium heat rather than microwaving which can make the pasta tough. Stir frequently until heated through and add a fresh drizzle of chilli oil just before serving to revive the bright heat.

Perfect Pairings

This pasta works wonderfully alongside a crisp green salad dressed simply with lemon juice and olive oil to cut through the richness. For wine pairings seek out a medium bodied red with good acidity like a Chianti or Sangiovese that can stand up to the spice but won't overpower the sweet onions. Alternatively a crisp dry white like Pinot Grigio provides refreshing contrast to the heat. For a complete meal consider adding a protein like grilled chicken or sautéed shrimp on top or mixing in white beans for a vegetarian option.

Variations To Try

This recipe provides an excellent base for countless variations. Try adding toasted pine nuts for crunch and nutty flavor. Mix in wilted spinach or arugula at the end for color and nutrition. For a more substantial dish stir in chunks of roasted eggplant or bell peppers with the onions. Replace some or all of the pasta water with cream for a more indulgent sauce. During summer months add halved cherry tomatoes that burst slightly in the residual heat. The versatility of this dish makes it perfect for adapting to seasonal produce or pantry limitations.

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Frequently Asked Questions

→ How do you caramelize onions perfectly?

Cook onions slowly over medium-low heat with olive oil, butter, and a pinch of salt, stirring occasionally. Add a bit of sugar for enhanced caramelization.

→ Can I adjust the spice level in this pasta?

Yes, you can control the heat by adjusting the amount of chili flakes used in the chili oil.

→ What type of pasta works best for this dish?

Spaghetti, fettuccine, or penne are great choices, but any type of pasta will work well.

→ Can I prepare the caramelized onions in advance?

Yes, you can make them ahead and store in the fridge for up to 2-3 days. Reheat when ready to assemble the dish.

→ What can I add to enhance the dish further?

Consider adding roasted vegetables like bell peppers or zucchini, or garnish with extra Parmesan or parsley for added flavor.