Caramelized Onion Pasta
Published
Published
Once you learn how to properly caramelize onions, it’s the gift that keeps on giving. This creamy caramelized onion pasta is glorious in every bite – the onions cook down into a rich, sweet sauce that clings to every strand of spaghetti, with Parmesan and a touch of olive oil bringing everything together. It tastes gourmet but is hardly any fuss, so it feels fancy enough for company but is simple enough for a weeknight dinner.
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Caramelized onions really are kitchen magic, and blending them into a sauce makes this recipe stand out from the usual chunky versions. I love how the onions transform into a silky gravy, giving the pasta that rich, creamy texture without a drop of heavy cream. It feels like a little splurge, but it’s simple, affordable, and beginner-friendly. I’ll share my favorite tips so you can nail the onions every time and even make the sauce ahead. Tossed with spaghetti and a good handful of Parmesan, this pasta is cozy, satisfying, and always a hit at the table.
Helpful Tips
- Cook onions low and slow. Patience is the secret here. If you crank up the heat, the onions will burn instead of turning that gorgeous golden brown. Give them time to soften and sweeten, and you’ll be rewarded with deep, rich flavor.
- Save that pasta water. Don’t pour it all down the drain! The starchy water is liquid gold and makes the sauce cling beautifully to every strand of pasta.
- Blend in stages. Start with less water and add more as you go. This way, the sauce turns out silky and luscious instead of thin and runny.
Caramelized Onion Pasta
Ingredients
- 4 tablespoons butter
- 4 large sweet onions, sliced thin
- 3 cloves garlic, minced
- 12 ounces dry spaghetti
- 1/2 cup olive oil
- 3 egg yolks
- 1 & 1/4 cups reserved pasta water
- 3/4 cup grated Parmesan
- salt and pepper, to taste
- fresh chopped parsley, for garnish
Instructions
- In a large nonstick skillet over medium heat, melt the butter. Once bubbly, add the sliced onions and sauté for 10 minutes. Reduce the temperature to medium-low and continue cooking, stirring every so often until caramelized, about 30 more minutes. Stir in the garlic until fragrant, 20-30 seconds.
- Toward the end of cooking the onions, prepare 12 ounces of dry spaghetti in salted boiling water and cook until al dente. Reserve 1 & 1/4 cups of the pasta water, then drain.
- In a blender, combine the caramelized onions, olive oil, egg yolks, Parmesan, 1 cup of pasta water, and salt and pepper. Blend until smooth. Add more water to thin it out, (only if necessary). Add water to the blender in stages, so the sauce isn't runny.
- Add warm cooked spaghetti and the onion sauce back to the skillet to warm through over low heat, about a minute.
- Garnish with fresh chopped parsley and enjoy!
Notes
- Slice the onions as evenly as you can so they caramelize at the same rate.
- Sub in your favorite pasta shape or use gluten-free pasta.
- Add an extra splash of pasta water when reheating to bring back the silky sauce.
Nutrition
Nutritional information given is an automatic calculation and can vary based on the exact products you use and any changes you make to the recipe. If these numbers are very important to you, I would recommend calculating them yourself.
Did you make this? Leave a rating below!How to Make Caramelized Onion Pasta Step by Step
Caramelize the onions: In a large nonstick skillet over medium heat, melt 4 tbsp butter. Once bubbly, add 4 large sweet onions, sliced thin, and sauté for about 10 minutes. Reduce the heat to medium-low and continue cooking, stirring occasionally, until the onions are deeply caramelized, about 30 more minutes. Stir in 3 cloves garlic, minced, and cook until fragrant, about 20–30 seconds.
Cook the pasta: While the onions finish cooking, bring a large pot of salted water to a boil. Add 12 ounces dry spaghetti and cook until al dente. Reserve 1¼ cups of the pasta water, then drain.
Blend the sauce: Transfer the caramelized onions to a blender. Add ½ cup olive oil, 3 egg yolks, ¾ cup grated Parmesan, 1 cup reserved pasta water, and a good pinch of salt and pepper. Blend until smooth, adding more pasta water a little at a time only if needed until the sauce is silky (not runny).
Combine the pasta and sauce: Return the warm cooked spaghetti and onion sauce to the skillet. Toss together over low heat just until warmed through, about 1 minute.
Garnish and serve: Garnish with fresh chopped parsley and extra Parmesan, if desired. Serve immediately. Enjoy!
Serving Suggestions
I usually pair this caramelized onion pasta with something fresh and simple on the side, like a crisp green salad with lemon vinaigrette. Garlic knots or my easy skillet breadsticks are perfect for soaking up every bit of that silky sauce. If I’m looking to round out the meal, I’ll add roasted green beans or Brussels sprouts. And when I want to make it extra hearty, I’ll top the pasta with sliced skillet steak or tender baked chicken breast—it turns this cozy dish into a full dinner that always satisfies.
How to Store Leftovers
Leftover caramelized onion pasta keeps in the fridge for up to 3 days, stored in an airtight container. When you’re ready to enjoy it again, warm it gently in the microwave or on the stove over low heat with a splash of pasta water or broth to loosen the sauce and bring back that silky texture. I don’t recommend freezing this dish since the sauce can separate after thawing.
More Comfort Food Pasta Recipes You’ll Love
- Creamy Ratatouille Pasta
- Creamy Penne with Tomatoes
- French Onion Mac and Cheese
- Lazy Day Lasagna
- Chicken Tetrazzini
I hope you love this delicious and easy recipe – be sure to give it a review below! Also don’t forget to follow Belly Full on TikTok, Instagram, Facebook, Pinterest, and YouTube!
Great recipe for low sodium families
You are so sweet, a treat to watch !