This creamy caramelized onion pasta is rich, luscious and packed with flavor. Sweet, jammy onions are cooked low and slow until deeply golden, then folded through a garlic parmesan cream sauce with a touch of thyme and lemon for balance. If you’ve ever wondered how to turn caramelized onions into a proper pasta sauce, this is the one to make.
Hi! This caramelized onion pasta came about as I recently wrote a recipe for a French Onion Mac and Cheese (which you should absolutely make too!) Yes, the onions take time but it's so worth it! The flavor they add is off the charts.
As always I have used my White Pasta Sauce as a base, it's the perfect creamy base with parmesan and garlic. If you’ve made any of my creamy pastas before, you’ll know I’m all about getting that perfect glossy sauce. This one is no different, just with the added bonus of those sweet caramelized onions.
Main ingredients
Pasta - Any pasta shape will work but I think the onions work so well with a long shape. I have used fettuccine but linguine or spaghetti would be great to.
Onions - I use brown/yellow onions here. They are perfect for caramelizing as they become really sweet and jammy when cooked low and slow. It might seem like a lot to start with but they cook down significantly.
Cream - I use heavy cream for the best flavor and stability. It creates a rich sauce but is balanced out with pasta water and lemon so it doesn’t feel too heavy.
Parmesan - Finely grate your own using a microplane or the star side of a box grater so it melts smoothly into the sauce. Pre-shredded cheese won’t give you the same result.
Garlic - Fresh garlic cloves are best here for that classic base flavor. Adjust the amount to your taste.
Thyme - Adds a subtle savory, slightly earthy note that balances the sweetness of the onions. You can leave it out if you prefer or substitute with rosemary.
How to make caramelized onion pasta
The full ingredient list and detailed method are in the recipe card below, this is for a visual reference.
1. Add the sliced onions to a pan with the butter and olive oil and cook over medium heat until softened.
2. Lower the heat and continue cooking, stirring regularly, until the onions are deeply golden, soft and jammy. Set aside.
3. In the same pan, melt the butter then add the garlic (and red pepper flakes if using) and cook gently until fragrant.
4. Pour in the cream, bring to a gentle simmer then add the parmesan, stirring until melted and smooth. Stir in the thyme and ¼ cup pasta water.
5. Add the cooked pasta and toss well.
6. Add the onions and lemon juice and let it bubble away over a low heat for 1-2 minutes. Season to taste.
Tips from Emilie
- Caramelize the onions low and slow. Don’t rush this step, deeply golden onions give the dish its signature flavor.
- Undercook your pasta. I under cook dried pasta by a minute from package instructions so it can bubble away in the sauce at the end.
- Grate the cheese yourself. Pre-shredded cheese contains anti-caking agents that stop the cheese melting smoothly into a sauce.
- Keep the heat gentle. Cream sauces should simmer softly, never boil. This keeps the sauce silky and prevents it from splitting.
- Always reserve some pasta water before draining. When mixed into the creamy sauce it helps it cling to the pasta. It's also handy to loosen if the sauce gets too thick.
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Common questions
Caramelizing onions usually takes 30-40 minutes over a low heat. The exact time can vary depending on your pan and heat level, so focus on them becoming deeply golden, soft and jammy rather than sticking to a strict time.
I always prefer a heavy cream as it is the most stable for cooking. It's easily adjustable with pasta water if you need to thin it down.
I actually have a cacio e pepe with caramelized onions which is made without cream and so delicious.
This pasta is best eaten fresh, but any leftovers can be stored in an airtight container in the fridge for 2-3 days. Reheat gently on the stove or microwave with a splash of water, milk or cream to loosen the sauce as it will thicken in the fridge.
Some other creamy pasta sauces to try
Did you make this recipe?
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Recipe
Creamy Caramelized Onion Pasta
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Ingredients
- 200 grams dried pasta (or 300 grams fresh)
For the onions
- 1 tablespoon olive oil
- 1 tablespoon butter
- 2 medium onions (mine weighed 450 grams total)
For the sauce
- 1 tablespoon butter
- 2 garlic cloves, minced
- ¼ teaspoon red pepper flakes (optional)
- ⅔ cup heavy cream
- 50 grams parmesan cheese, very finely grated
- 1 tablespoon fresh thyme leaves, roughly chopped
- 1 tablespoon lemon juice, plus zest to serve
- salt and pepper to taste
Instructions
Caramelize the onions
- Trim both ends off the onions then cut in half lengthways, peel, then lay each half flat and slice into ¼-inch thick half circles
- Heat 1 tablespoon of olive oil and 1 tablespoon of butter in a heavy bottomed skillet or Dutch oven over a medium heat and cook the onions for 10 minutes until softened.
- Mix the salt through then lower the heat down to low and continue cooking for 40 minutes until golden and super soft. It needs to be stirred often so they don't catch and burn.
- Add a small splash of water if they are getting too dry. Set aside when done.
Cook the pasta
- Boil your pasta in well salted boiling water, I usually undercook by 1 min from package instructions. Reserve a cup of pasta water before draining.
Make the sauce
- When the pasta only has about 5 minutes to go return the skillet you cooked the onions in to medium heat. Add the garlic (and red pepper flakes if using) and cook gently for 1 minute until fragrant, it shouldn’t brown at all.
- Pour in the cream and bring to a very gentle simmer, lowering the heat if needed so it never boils. Stir in the thyme.
- Add the parmesan in 2-3 additions, mixing well and letting it melt between each addition until the sauce is smooth.
- Add the cooked pasta, caramelized onions, lemon juice and ¼ cup pasta water and toss well.
- Let it gently bubble away for a minute or two over a low heat so the pasta finishes cooking and the sauce thickens, adding more pasta water if needed to loosen. It will thicken quickly off the heat so keep it on the saucy side in pan.
- Check for seasoning and serve immediately with extra parmesan and grated lemon zest if desired.
Video
Notes
Hi, I'm Emilie
I've spent years testing pasta doughs, sauces, and weeknight favorites so you don't have to. Everything on The Burnt Butter Table is designed to be simple, comforting, and unbelievably delicious.
Tina says
Absolutely spectacular! I added chicken breast (a girl’s got protein goals to hit) and the whole family, including my toddler, devoured this! I used fresh pasta and I think that bumped it up a notch, but the sauce is simply amazing. Do not skip the time needed to really caramelize the onions!
Emilie Pullar says
Adding chicken is so perfect with this recipe! Thank you so much for making and coming back to review Tina, appreciate it so much 🙂