Skip to main content

Cauliflower and Caramelized Onion Tart

This elegant cauliflower and caramelised onion tart combines earthy roasted vegetables with a rich, silky custard. The addition of truffle oil adds a luxurious depth of flavour that perfectly complements the nutty notes of Gruyère and Parmesan cheese. Golden, crisp pastry provides the ideal vessel for the sweet, slow-cooked onions and mascarpone filling, making this a truly indulgent savoury centerpiece.

Designed as a sophisticated vegetarian main or a standout lunch dish, this tart is excellent for entertaining as the elements can be prepared in advance. The combination of sweet onions and roasted cauliflower offers a wonderful balance of textures. Serve it warm with a crisp green salad and a sharp vinaigrette to cut through the richness of the Italian cream cheese and indulgent double cream.

Continue reading below

Ingredients for Cauliflower and Caramelized Onion Tart

  • 1 small head of cauliflower (about 450g ), cored, cut into 1-inch florets

  • 40ml olive oil, divided

  • 1 tablespoon truffle oil*

  • 1 refrigerated pie crust

  • 1 large onion, halved lengthwise, thinly sliced

  • 1 tablespoon Dijon mustard

  • 2 large eggs

  • 1 (7- to 230g ) container mascarpone cheese (Italian cream cheese)*

  • 120ml whipping cream

  • 1/4 teaspoons ground white pepper

  • Pinch of ground nutmeg

  • 120g grated Gruyère cheese

  • 90g grated Parmesan cheese

  • *Available at some supermarkets, specialty foods stores, and Italian markets nationwide.

How to make Cauliflower and Caramelized Onion Tart

Position rack in centre of oven; preheat to 218°C. Toss cauliflower with 1 tablespoon olive oil in large bowl. Spread on large rimmed baking sheet, spacing apart. Sprinkle with salt and pepper. Roast 15 minutes; turn florets over. Continue roasting until tender, about 25 minutes longer. Cool cauliflower, then thinly slice. Drizzle with truffle oil; toss. Reduce oven temperature to 177°C.

Press pie crust onto bottom and up sides of 9-inch-diameter tart pan with removable bottom. Line pie crust with foil; fill with pie weights. Bake crust 20 minutes. Remove foil and pie weights; bake until crust is golden, about 5 minutes, pressing crust with back of fork if bubbles form. Cool crust. Maintain oven temperature.

Heat remaining 1 1/2 tablespoons olive oil in heavy large skillet over medium heat. Add onion; sprinkle with salt and pepper. Cook until onion is deep golden brown, stirring occasionally, about 40 minutes. Cool slightly. DO AHEAD Can be made 1 day ahead. Store crust at room temperature. Cover and chill cauliflower and onion separately.

Brush bottom and sides of crust with mustard. Spread onion in crust. Arrange cauliflower evenly over. Set tart on rimmed baking sheet. Whisk eggs and next 4 ingredients in medium bowl. Stir in Gruyère. Pour mixture over filling in tart pan; sprinkle with Parmesan. Bake until tart is golden and centre is set, about 40 minutes. Transfer to rack; cool 15 minutes before serving.

Disclaimer

While every effort has been made to ensure the information is accurate and up to date, individual needs may vary and dietary requirements can differ based on personal health conditions. Always check food labels and allergen information before preparing or consuming any recipe. If you have specific health concerns, allergies, intolerances, or are following a medically prescribed diet, seek advice from your GP, pharmacist, or a registered dietitian before making significant changes to your diet or lifestyle.

Article history

The information on this page is peer reviewed by qualified clinicians.

  • 17 Jan 2026 | Originally published

    Authored by:

    UK recipe editors

    Peer reviewed by

    UK recipe editors
flu eligibility checker

Ask, share, connect.

Browse discussions, ask questions, and share experiences across hundreds of health topics.

symptom checker

Feeling unwell?

Assess your symptoms online for free

Sign up to the Patient newsletter

Your weekly dose of clear, trustworthy health advice - written to help you feel informed, confident and in control.

Please enter a valid email address

By subscribing you accept our Privacy Policy. You can unsubscribe at any time. We never sell your data.