Bucatini with Tomato, Butter, and Onion Sauce

Why You’ll Love This Recipe

• Deep flavor from just five main ingredients, thanks to a slow, gentle simmer.
• Silky, glossy sauce that hugs every strand of bucatini without being heavy.
• Hands-off cooking: the onion simmers in halves, then gets removed—no chopping needed.
• Weeknight-easy yet dinner-party elegant, finished with fresh basil.

Grocery List

• Produce: 1 large yellow onion; 1 small bunch fresh basil
• Dairy: Unsalted butter; Parmigiano Reggiano (optional)
• Pantry: 28 oz can whole peeled tomatoes; bucatini; kosher salt; fine sea salt; black pepper (optional); pinch of sugar or red pepper flakes (optional)

Full Ingredients

Tomato–Butter–Onion Sauce

• 28 oz (800 g) can whole peeled tomatoes, with juices (preferably San Marzano)
• 5 tbsp (70 g) unsalted butter
• 1 large yellow onion (10–12 oz / 280–340 g), peeled and halved lengthwise
• 1 tsp fine sea salt, plus more to taste
• Pinch of sugar, only if needed to balance acidity (optional)
• Freshly ground black pepper, to taste (optional)

Pasta & Finish

• 12 oz (340 g) bucatini
• 4 qt (3.8 L) water + 2 tbsp kosher salt for boiling
• 12–15 fresh basil leaves, torn
• Finely grated Parmigiano Reggiano, for serving (optional)

Step-by-Step Instructions

Step 1: Prep the minimal ingredients

Peel the onion and halve it lengthwise through the root. Open the tomatoes and, if desired, crush them lightly by hand in the can or leave them whole to break up in the pot. Measure the butter. Set a large pot with 4 quarts of water over high heat and cover so it comes to a boil faster.

Step 2: Start the sauce

In a 3- to 4-quart saucepan, combine the tomatoes with their juices, butter, onion halves (cut sides down), and 1 teaspoon fine sea salt. Bring to a gentle simmer over medium heat, 3–5 minutes, stirring occasionally and breaking up the tomatoes with a spoon or potato masher.

Step 3: Simmer low and slow

Reduce heat to medium-low and simmer the sauce uncovered for 35–45 minutes, stirring every 5–7 minutes. Aim for small, lazy bubbles (about 190–200°F if you check with a thermometer). The sauce should thicken, turn glossy with butter, and reduce by roughly one-third. Avoid a hard boil, which can break the emulsion. Taste; add a pinch of sugar only if the tomatoes are very tart.

Step 4: Boil the bucatini

When the sauce is about 10 minutes from done, salt the boiling water with 2 tablespoons kosher salt. Add the bucatini and cook until 1 minute shy of al dente, usually 8–9 minutes (check your package). Reserve 1 cup (240 ml) of the starchy pasta water, then drain.

Step 5: Marry pasta and sauce

Remove and discard the onion halves from the sauce (or save for another use). Add the drained bucatini to the sauce along with 1/2 cup pasta water. Toss vigorously over medium heat for 1–2 minutes until the sauce emulsifies and clings to the pasta. Add more pasta water a splash at a time if it looks dry. Season with salt and black pepper to taste. For extra silkiness, swirl in 1 tablespoon more butter (optional).

Step 6: Finish with basil and serve

Off the heat, fold in the torn basil. Twirl the bucatini into warm bowls, spooning over any sauce left in the pan. Serve immediately, passing extra basil, black pepper, and finely grated Parmigiano Reggiano at the table if you like.

Pro Tips

• Quality tomatoes matter: whole peeled tomatoes (ideally San Marzano) give the cleanest, sweetest flavor.
• Leave the onion in big halves—they quietly perfume the sauce and are easy to remove.
• Simmer uncovered and gently; you want reduction without aggressive boiling to keep the sauce glossy.
• Salt the pasta water generously so the bucatini is seasoned within, not just on the surface.
• Use pasta water to adjust consistency—the starch helps the butter-tomato emulsion cling beautifully.

Variations

• Spicy: Add 1/2 teaspoon red pepper flakes to the sauce at the 10-minute mark for gentle heat.
• Garlic-kissed: Sizzle 1 lightly crushed garlic clove in 1 tablespoon butter for 1 minute, then add tomatoes, remaining butter, and onion as directed. Remove garlic with the onion.
• Rosé twist: Stir in 2 tablespoons heavy cream off heat for a blush-colored, ultra-silky finish.

Storage & Make-Ahead

The sauce (without pasta) keeps 4–5 days refrigerated or up to 3 months frozen. Cool completely, remove the onion, and store airtight. Reheat gently over low heat with a splash of water. Cook pasta fresh and combine just before serving. Leftover sauced pasta is best within 1 day; reheat with a few tablespoons water over medium-low, tossing until the sauce loosens.

Nutrition (per serving)

Approximate values: 460 calories; 16 g fat; 69 g carbohydrates; 11 g protein; 4 g fiber; sodium varies by salt and tomatoes. Values are estimates and will vary with ingredients and portion size.