Easy cacio e pepe with caramelized onions

A cacio e pepe style sauce with caramelized onions for the ultimate flavour bomb! A simple recipe that results in a creamy cheese sauce loaded with pepper and sweet caramelized onions. My take on the classic Italian pasta dish (with a little butter, the purists will hate me!). You'll be eating it straight out of the skillet, I promise!

Hello! If you know me at all you'll know cacio e pepe pasta is my death row dish (with a side of fried chicken please!). I make no apologies for using a butter base, I never claim to be traditional and this is just the way I like to make it. I have a plain cacio e pepe recipe or another combination which is to die for is my cacio e pepe with olives and basil.

Sweet caramelized onions are such a delicious addition to this simple dish and the perfect contrast to lots of black pepper and salty parmesan cheese. I have used a hand rolled pici, which is one of the easiest pasta shapes to make. It requires little to no special equipment and is made with flour, water and olive oil. This sauce will work with any long noodle shape you like though, fresh or dried.

Ingredients

Onions - I use brown/yellow onions. This is the time consuming part of the recipe but I promise, it's worth it!

Balsamic glaze - I love adding some sticky balsamic glaze (a thick, slightly sweetened balsamic vinegar) to the onions at the end. You could use regular balsamic vinegar or leave it out altogether.

Butter - As I said, I just prefer making cacio e pepe with butter, I know it's not traditional. Use unsalted butter or regular.

Pepper - Freshly cracked black peppercorns are best. I have specified 2 teaspoons but use more if you like!

Starchy pasta water - The key to thickening the sauce. It pays to not overfill your pot of water as the starchier the water the better.

Parmesan cheese - I have used all parmesan as that is generally what I have. You could use pecorino romano cheese (more of a sharp flavor) or a 50/50 mixture of both. Please don't buy pre-grated cheese, it's usually full of additives.

How to get the perfect silky sauce

Cacio e pepe is one of the most simple pasta dishes as it has such few ingredients, but it happens to be one of the hardest to make. There are SO many methods for getting the cheese to melt into the sauce and this method will become your go to. When made incorrectly, the parmesan can turn into a clumpy mess and go stringy, it won't happen with this cooking process.

• Firstly, I like to blend my parmesan cheese in a smoothie maker (I use a mini bullet one). The blade cuts the cheese up into a crumb/powder and it melts so much easier. Finely grated cheese is an absolute must so use a microplane or the star side of your box grater if you don't have a smoothie maker.
• When you add the starchy pasta water it needs a really good shake and whisk to make an emulsified sauce with the butter. I like to use a flat whisk.
• Shake the pan and whisk at the same time to get the liquids to blend. Don't be afraid to really agitate quite vigorously.
• When you add the pasta in, give it a really good toss then let it bubble away for a minute or two on a medium heat to thicken slightly.
• Then on a very low heat, sprinkle the cheese in an even layer on top of the pasta and leave it alone! Let it melt very gently for a minute and then go in with tongs and toss it over and over until a silky smooth sauce appears! Having it on a low heat here will make sure the pasta doesn't stick to the bottom of the pan.

How to caramelize onions

Caramelized onions are just so damn delish! I fell in love with them in a Pasta Social Club dish where she mixed them into a super cheesy white sauce. They take a little time but you could always cook them the day before and store in the fridge.

1. Cut both ends off the onions, peel and then halve lengthways.
2. Slice them into thin half circles about ¼ inch.
3. Heat the butter in a Dutch oven or large skillet (with a heavy bottom) and cook the onions over a medium-high heat until soft, about 10 minutes.
4. Add a good couple of pinches of salt and toss well.
5. Turn the heat right down and then cook until soft and golden. You'll need to keep an eye on them and stir every couple of minutes. If they are catching on the bottom the heat needs to be lower. It depends on your stove, mine take about 35 minutes.
6. I add a sweet balsamic glaze at the end to really enhance the sweetness.

Other tips for success

• Even if you use a large pot to cook the pasta in, don't overfill it. This is a sauce where you rely on the starchy pasta cooking water, you don't want to dilute all that starch in lots of water.
• If this is your first time making this then you might want to cook your pasta first. Reserve a big cup of pasta water then toss the drained pasta in a teaspoon of butter to stop it sticking and overcooking. Next time you'll be used to the timing so you'll know when to put your pasta on to time it perfectly.
• Weigh your pasta out so there is a perfect ratio of sauce to pasta. I use 150 grams fresh pasta per person or 100 grams dried pasta per person.
• Heat your plates! Pasta gets cold really quickly so I always have my plates or pasta bowls in a warm oven while I cook.

Making pici pasta

Pici is hands down one of my favourite pasta shapes. I first had it in Tuscany and the irresistible chewy texture won me over instantly. It is a hand rolled spaghetti shape and is made from flour, water and olive oil. You roll it out by hand and it's a fun activity for the whole family! Check out my easy recipe and guide for hand rolled pici pasta.

Recipe FAQs

Want some other recipes to try?

I have all sorts of delicious recipes to try. If you loved this cacio e pepe with caramelized onions then PLEASE try my version with Basil and Olives, it's to die for. For another peppery dish try my Easy Creamy Peppery Pasta Sauce. One of my most recent favorites is my Sausage Pasta Bake, the ultimate comfort food!

Made this recipe and loved it?

I would love love LOVE if you could leave me a review down below and let me know what you thought! I love to hear any changes or adaptions you have made too. Also if you put a photo on instagram, please tag me so I can see, it makes my day!

Recipe

Easy cacio e pepe with caramelized onions

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5 from 8 votes

Author: Emilie Pullar

Prep time:15 minutes minutes

Cook Time:45 minutes minutes

Servings: 2 people

Print Recipe Pin Rate

A cacio e pepe style sauce with caramelized onions for the ultimate flavour bomb! A simple recipe that results in a creamy cheese sauce loaded with pepper and sweet caramelized onions.

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Ingredients

• 2 tablespoons butter
• 2 brown or yellow onions see notes
• 2 teaspoons balsamic glaze see notes
• 300 grams fresh pasta or 200 grams dried pasta
• 80 grams butter
• 2 teaspoons freshly cracked black pepper more if you like
• ½ cup pasta water
• 70 grams parmesan finely grated, see notes

Instructions

For the onions:

• Cut both ends off the onions then cut in half lengthways, peel and then slice in half circles ¼ inch thick.
• Melt the 2 tablespoons of butter in a heavy bottomed skillet or dutch oven over a medium high heat and cook the onions for 10 minutes until softened. Stir them so they don't catch.
• Season with a good couple of pinches of sea salt and then turn the heat down to low and continue cooking for 30 minutes (it might take longer depending on your stove top) or until golden and super soft. You'll want to stir every couple of minutes, they mustn't burn so try and have the heat as low as possible.
• Add the balsamic, mix well and continue cooking for 5 minutes then set aside.

For the sauce

• Get a pot of well salted water boiling and depending on whether you are using fresh or dried pasta will dictate when you add the pasta to the water. The sauce only takes a few minutes to bring together so when using fresh pasta I add the pasta to the water when the butter is just starting to melt.
• Melt your butter in a large skillet over medium - high heat and add the pepper.
• Let it sizzle together for a minute then turn down the heat to low.
• Add ½ cup pasta water and whisk vigorously to emulsify. I like to shake the pan with my left hand and whisk with my right to agitate it quite vigorously. It should be simmering very gently.
• Keep agitating the pan and whisking until it thickens slightly 1 - 2 minutes.
• Add your cooked pasta into the pan, toss with the liquid and let it bubble away gently for a minute or so.
• Arrange the pasta into an even layer in the pan and then sprinkle the cheese over top in an even layer over top.
• Leave it alone and let it melt gently on top for a minute or so, the heat should be nice and low so the pasta doesn't stick to the pan. Give the pan a shake if you are worried it is sticking.
• Then with tongs toss the pasta over and over quite quickly until a silky sauce appears. 
• Add the onions in and give it a quick toss then serve immediately.

Notes

• If you are USA based you might not realise your onions are huge! Just use one whole onion. 
• Balsamic glaze is a thickened and slightly sweet balsamic vinegar. It is easy to find in supermarkets but sub for balsamic vinegar or leave it out if you wish.
• Add more pepper if you wish!
• You could use pecorino if you prefer or a 50/50 split of pecorino and parmesan.
• If you make the onions ahead, give them a 20 second burst in the microwave before adding them into the pasta. It will mean they mix through easier if warm.

Author: Emilie Pullar

Prep Time: 15 minutes minutes

Cook Time: 45 minutes minutes

Course: Vegetarian

Cuisine: Italian Inspired

Keyword: cacio e pepe, caramelized onions, pasta

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