Caramelized Onion Pasta with Silky Fettuccine Tips, FAQ & printable recipe

Tips for success

For the best caramelization, resist the urge to stir the onions constantly. Let them sit in the pan for a few minutes at a time, then stir, so they can develop a deep brown color.

If they start to stick, add a tablespoon of water and scrape up the browned bits—this deglazing adds flavor to the sauce.

When tossing the pasta, use tongs and a lifting motion rather than stirring. This helps the sauce emulsify and coat the noodles evenly. If the sauce seems too thick, add pasta water a tablespoon at a time until it reaches the desired consistency. The sauce should be silky and glossy, not watery.

Variations

• Add Bacon: Cook 4 slices of chopped bacon in the skillet until crisp, then remove and set aside. Use the bacon fat in place of half the butter, and toss the cooked bacon back in with the pasta.
• Herb Infusion: Add a sprig of fresh thyme or a few sage leaves to the butter as it melts. Remove the herbs before adding the pasta, or leave them for a more rustic look.
• Vegan Version: Replace the butter with a high-quality vegan butter or olive oil, and use a vegan Parmesan alternative. The rest of the recipe stays the same.
• Add Mushrooms: Slice 8 oz of cremini mushrooms and sauté them with the onions during the last 10 minutes of caramelization. They add an earthy depth that pairs well with the sweet onions.

Storage and make-ahead

Fridge

Store leftovers in an airtight container in the refrigerator for up to 3 days. Reheat gently with a splash of water or broth.

Freezer

Caramelized onions can be frozen for up to 3 months. The pasta itself is not ideal for freezing.

Reheat

Reheat pasta in a skillet over medium-low heat with a splash of water or milk, tossing until hot and glossy.

Leftover pasta can be stored in an airtight container in the refrigerator for up to 3 days. To reheat, place it in a skillet over medium-low heat with a splash of water or milk, tossing until warmed through.

The sauce may tighten when chilled, so adding a little liquid helps restore its silky texture.

The caramelized onions can be made up to 3 days ahead and stored in the refrigerator. Reheat them gently in a skillet before adding the pasta.

The pasta itself is best cooked fresh, but you can cook it a day ahead, toss it with a little olive oil, and refrigerate it in a sealed bag. When ready to serve, plunge it into boiling water for 30 seconds to warm it, then toss with the onions.

Serving ideas

Serve the pasta immediately after tossing, while it's hot and the sauce is at its silkiest. Twirl each portion into a neat nest using tongs or a fork, and place it in a warmed bowl. Top with a generous shower of shaved Parmesan and, if desired, a few cracks of black pepper.

This pasta pairs beautifully with a crisp green salad dressed with lemon vinaigrette, or with a simple side of sautéed spinach.

A glass of dry white wine, such as Pinot Grigio or Sauvignon Blanc, complements the sweet onions and buttery sauce. For a heartier meal, serve it alongside grilled chicken or shrimp.

Frequently asked questions

Recipe card

Caramelized Onion Pasta with Silky Fettuccine

Prep 10 minCook 30 minTotal 40 minServes 4

Ingredients

• 3 large sweet yellow onions, thinly sliced
• 4 tbsp unsalted butter
• 1/2 tsp kosher salt, plus more for pasta water
• 10 oz fettuccine
• 1/2 cup shaved Parmesan cheese, for serving

Instructions

1. Cut the sweet onions in half through the root end, then peel them. Slice each half crosswise into thin crescents, about 1/8 inch thick. Keep the slices uniform so they cook evenly.
2. Set a large skillet over medium-low heat and add the butter. Let it melt slowly, swirling the pan occasionally, until it is fully melted and just starting to foam.
3. Add the sliced onions to the skillet and toss them with the butter until every slice is coated. Spread them into an even layer. Cook over medium-low heat, stirring occasionally, for 25 minutes, until the onions are deep amber, very soft, and have released a glossy, sticky glaze.
4. While the onions caramelize, bring a large pot of salted water to a boil. Add the fettuccine and cook according to package directions until al dente. Reserve 1 cup of pasta water, then drain the pasta.
5. Add the drained fettuccine to the skillet with the caramelized onions. Turn the heat to medium-low. Using tongs, toss the pasta with the onions and glaze for 1 to 2 minutes, adding splashes of reserved pasta water as needed to create a silky sauce that coats every strand.
6. Remove the skillet from the heat. Add half of the shaved Parmesan and toss once more. Serve immediately in warm bowls, twirling the pasta into nests, and top with the remaining Parmesan.

Contains: gluten, milk

Estimated nutrition per serving

Calories

420

Protein

12 g

Carbohydrates

58 g

Fat

16 g

Automatic estimate from the ingredient list, not laboratory-verified.