Dinner

Caramelized Onion Pasta Recipe

ByJulian Dempsey December 27, 2025December 27, 2025

Introduction

This caramelized onion pasta is a simple yet indulgent dish that highlights the sweet, deep flavors of slowly cooked onions. With a creamy Parmesan sauce brightened by lemon and parsley, it’s perfect for a cozy dinner for two.

A white speckled plate holds a serving of creamy pasta with caramel-colored onion sauce mixed throughout the long, flat noodles. The pasta sits slightly twisted in the center of the plate, topped with finely grated white cheese and small green parsley leaves scattered evenly over the dish. The edges of the plate show dark brown speckles, adding a rustic touch. The plate rests on a white marbled surface, with a piece of hard cheese and a metal grater to the left, and a black fork to the right. Light shines softly on the pasta, highlighting the smooth texture of the sauce and the shine on the noodles. photo taken with an iphone --ar 4:5 --v 7

Ingredients

2 Tbsp. extra-virgin olive oil
2 Tbsp. unsalted butter
2 lb. sweet or yellow onions (about 4 large), thinly sliced
1 1/2 tsp. kosher salt, plus more
4 garlic cloves, finely chopped
8 oz. linguine or other long strand pasta
4 oz. Parmesan, finely grated (about 2 cups), plus more for serving
½ lemon
½ cup finely chopped parsley

Instructions

Step 1: Heat the olive oil and butter in a medium Dutch oven or heavy pot over medium heat until the butter melts. Add the sliced onions, 1 ½ teaspoons kosher salt, and a pinch of freshly ground black pepper. Cook, stirring occasionally, until the onions are very tender and a deep golden brown, about 30 minutes. Add the chopped garlic and cook for about 1 minute until fragrant.
Step 2: While the onions cook, bring a large pot of salted water to a boil. Cook the linguine until very al dente, about 2 minutes less than the package directions. Reserve 1 ½ cups of the pasta cooking water and drain the pasta.
Step 3: Add the cooked pasta and 1 cup of the reserved pasta water to the onion mixture. Stir to combine. Add a handful of the grated Parmesan and stir until melted. Continue adding the cheese in small handfuls, stirring between additions and adding more pasta water as needed until a glossy sauce forms and coats the pasta.
Step 4: Squeeze the juice of half a lemon into the pasta and stir in the chopped parsley. Taste and adjust seasoning with additional pepper if desired. Divide the pasta among shallow bowls, topping each with additional Parmesan and freshly ground black pepper.

Tips & Variations

Use sweet onions like Vidalia or Walla Walla for a more mellow, sweeter flavor during caramelization.
For a richer sauce, stir in a splash of heavy cream along with the Parmesan cheese.
Try adding toasted pine nuts or crispy pancetta for added texture and flavor.

Storage

Store any leftover caramelized onion mixture in an airtight container in the refrigerator for up to 5 days or freeze for up to 3 months. Reheat gently on the stove, adding a splash of water or pasta cooking liquid to loosen the sauce if needed. Cook fresh pasta to serve for best texture.

How to Serve

A white speckled plate contains a serving of linguine pasta coated in a creamy light brown sauce with visible soft caramelized onion slices mixed throughout. The pasta strands, pale yellow in color, are loosely twirled in the center of the plate, sprinkled with finely chopped green parsley and tiny shreds of white grated cheese. Small black pepper flakes are scattered on top, adding contrast to the dish. Next to the plate, on a white marbled surface, there is a block of hard cheese with some grating near a metal grater, and a black fork is placed on the right side. photo taken with an iphone --ar 4:5 --v 7

Serve this delicious recipe with your favorite sides.

FAQs

Can I use a different type of pasta?

Yes, any long strand pasta like spaghetti or fettuccine works well with this recipe. Just adjust the cooking time according to the package instructions.

How do I know when the onions are properly caramelized?

The onions should be very tender and have a deep golden brown color. This usually takes around 30 minutes of cooking over medium heat with occasional stirring.