Tart featuring cauliflower and sweet caramelized onions

Decadent Cauliflower and Caramelized Onion Tart

This exquisite tart is the epitome of culinary elegance. While you might enjoy it for a casual Thursday dinner paired with a mountain of fresh salad, it’s truly fit for a delightful ladies' lunch or a special brunch gathering. The allure lies in its rich flavors, supplemented by luxurious ingredients such as truffles, dual types of cream, and a medley of cheeses, alongside the sweet depth of thirty-minute caramelized onions. Indulging in this dish while watching your favorite shows makes it a unique treat that feels just right.

Time, Ingredients, and Tips

This mouthwatering tart serves 8 and is perfect for sharing. Below are the details you’ll need to create this culinary masterpiece.

• 1 small head of cauliflower (approx. 1 pound) or one large head, chopped into 1-inch florets (consider vibrant Romanesco varieties for added flair)
• 1/2 tablespoons olive oil
• 1 tablespoon truffle oil or a few pinches of truffle salt (optional)
• 1 store-bought pie crust or homemade tart shell (recipe included)
• 1 large onion, sliced thin after halving
• 1 tablespoon Dijon mustard
• 2 large eggs
• 1 (7- to 8-ounce) container of mascarpone cheese
• 1/2 cup whipping cream (variations can include any low- or full-fat milk)
• 1/4 teaspoon either black or white pepper
• A pinch of nutmeg
• 1 cup grated Gruyère cheese (Swiss or Comté are excellent alternatives)
• 1/3 cup Parmesan cheese

As for preparation, start by positioning your oven rack to the center and preheating it to 425°F. In a mixing bowl, combine the cauliflower with 2 tablespoons of olive oil, then spread onto a rimmed baking sheet. Season with salt and pepper before roasting for 15 minutes. Flip the florets and continue roasting until golden and tender—an additional 15 minutes in my oven or 25 by the original estimate. Allow to cool, then slice thinly; drizzle with truffle oil or sprinkle with truffle salt if desired. Reduce your oven temperature to 350°F.

If you're opting for a store-bought crust, fit it into a 9-inch tart pan and line with foil before adding pie weights. Bake for 20 minutes, then remove the foil and bake until golden (around 5 more minutes). If bubbles appear, simply press them down with a fork. Let the crust cool while you maintain the oven's heat.

To caramelize the onions, heat the remaining olive oil in a large skillet over medium-low heat. Add the onions, season with salt and pepper, and cook until they’re a deep golden hue—this may take about 30 minutes. Once done, let them cool slightly.

Spread the mustard on the bottom and sides of the cooled crust, followed by the caramelized onions and then arrange the roasted cauliflower on top. Place your tart on a rimmed baking sheet to catch any potential spills. In a medium bowl, whisk the eggs, mascarpone, cream, pepper, and nutmeg together; fold in the Gruyère. Pour this creamy mixture over the tart in the pan and finish with a sprinkle of Parmesan. Bake for about 40 minutes until the tart is golden and the filling has set. Cool for 15 minutes before serving.

Prep Ahead: Feel free to caramelize the onions, par-bake the dough, and roast the cauliflower a day in advance to save time. Store the pie crust at room temperature, with the unbaked dough and veggies kept separately in the fridge. You can even prepare the entire tart a day early; just reheat it in a low oven before serving.

A Simple yet Delightful Tart Shell

This tart shell holds its form beautifully in the oven without needing to be par-baked, plus it hardly shrinks while baking—an instant win!

• 1/4 cups flour
• 1 tablespoon plus 2 teaspoons cornstarch
• 1/4 teaspoon salt
• 6 tablespoons butter, diced
• 1 egg

Begin by mixing the flour, cornstarch, and salt in a large bowl. Cut in the butter until you have tiny bits. Introduce the egg and mix with a fork until a dough forms. If it’s too crumbly, knead it together on a surface. You could also employ a food processor or mixer if preferred. Roll the dough onto a floured surface to create a 12-inch circle. Fit it into a 9-inch tart pan, crimping the edges and then chilling for 30 minutes before continuing with your filling—no par-baking necessary!