Cheddar Gorge Cheese Tart with Caramelized Onions

This savory cheddar tart pairs sharp, cave-aged cheddar with slowly caramelized onions in a crisp pastry shell. Inspired by the tangy, robust cheeses associated with Cheddar Gorge in Somerset, England, it makes a satisfying lunch or a simple supper with salad; use a mature farmhouse cheddar if the named regional cheese is unavailable.

Ingredients

1 sheet refrigerated pie pastry, about 9 inches (23 cm) across, or 1 homemade pastry crust
2 medium yellow onions, thinly sliced, about 3 cups (330 g)
1 tablespoon (15 ml) olive oil
1 tablespoon (14 g) unsalted butter
1 teaspoon (5 ml) balsamic vinegar
1 teaspoon (2 g) fresh thyme leaves, plus a little extra to garnish
3 large eggs (about 150 g without shells)
¾ cup (180 ml) heavy cream
½ cup (120 ml) whole milk
1½ cups (150 g) finely grated mature cheddar, preferably a sharp Cheddar Gorge farmhouse cheddar
¼ teaspoon (1 g) fine salt, plus more for the onions if needed
¼ teaspoon (0.5 g) freshly ground black pepper
⅛ teaspoon (0.25 g) ground nutmeg, optional

Instructions

Prepare the crust. Heat the oven to 375°F (190°C). Fit the pastry into a 9-inch (23 cm) tart pan, pressing it gently into the corners without stretching it. Trim the edge and prick the base several times with a fork. Line with parchment and fill with pie weights or dried beans. Bake for 12 minutes, then lift out the parchment and weights and bake for 5 minutes more, until the base looks dry but is not deeply browned. Set aside.
Caramelize the onions. While the crust bakes, heat the olive oil and butter in a wide skillet over medium-low heat. Add the sliced onions with a pinch of salt. Cook for 18–22 minutes, stirring every few minutes, until soft and golden brown. Lower the heat if the edges begin to scorch. Stir in the balsamic vinegar and thyme, cook for 1 minute, then take the pan off the heat. Spread the onions over the pastry base.
Mix the filling. In a bowl, whisk the eggs, cream, milk, salt, pepper and nutmeg, if using, until combined. Stir in the grated cheddar, keeping a small handful aside for the top if you like. Pour the mixture over the onions and gently shift the pan so the filling settles evenly. Sprinkle on the reserved cheese.
Bake until set. Bake at 375°F (190°C) for 28–33 minutes, until the edges are puffed and lightly golden and the center has only a slight wobble. For a food-safety check, the egg filling should reach 160°F (71°C); USDA FSIS identifies this as the safe minimum for egg dishes. Check in the center with an instant-read thermometer without touching the pan base.
Rest and serve. Cool the tart in its pan for 10 minutes so the filling can settle. Remove the outer ring, if using a tart pan with a removable base, and cut into six wedges. Scatter with a few thyme leaves and serve warm or at room temperature.

Tips

Grate cheddar from a block. Pre-shredded cheese often contains anti-caking agents and may not melt as smoothly. A mature farmhouse cheddar gives the filling a fuller, tangier flavor; any sharp cheddar is a practical substitute.
Keep the onions on gentle heat. Caramelization takes patience. If they brown too quickly, turn the heat down and add a teaspoon of water to loosen browned bits rather than letting them burn.
Prevent a soggy bottom. Blind-bake the crust until it looks dry, and let the onions cool slightly before adding them. If using a metal pan, place it on a preheated baking sheet for a crisper base.
Mind the salt. Aged cheddar can be salty, so start with the amount listed and taste the onion mixture before assembling. Avoid adding much extra salt to the custard.

Serving Suggestions

Serve a warm wedge with peppery greens dressed in lemon juice and olive oil, or with a tomato and cucumber salad for a lighter meal. A bowl of vegetable soup makes it more substantial, especially on a cool day. For a picnic or buffet, let the tart cool completely and cut it into smaller slices; it holds together better once the filling has settled.

Since the cheese is rich and savory, keep sides fresh and simply seasoned. Pickled onions, sliced apples or a spoonful of chutney make pleasant accompaniments. If serving a crowd, offer extra salad and serve the tart in modest wedges rather than adding more cheese to the filling.

Variations

Make it without a pastry crust: Butter a 9-inch (23 cm) pie dish, add the onions and cheese, then pour in the custard. Bake until the center is set and reaches 160°F (71°C); it will be softer and closer to a crustless quiche.

Add greens: Wilt 2 cups (60 g) baby spinach in the onion pan, then squeeze out excess liquid before arranging it in the crust. This adds color and a mild vegetal note without changing the basic method.

Use leeks instead: Substitute 2 medium leeks, cleaned and thinly sliced, for the onions. Cook them over medium-low heat until very soft and sweet; their flavor is gentler, so retain the balsamic vinegar for contrast.

Adjust the cheese: Replace up to half of the cheddar with grated Gruyère for a nuttier, milder tart. If Cheddar Gorge cheese is not available, choose a mature English farmhouse cheddar or another sharp, well-aged cheddar rather than a very mild cheese.

Storage and Reheating

Refrigerate the tart within 2 hours of baking, in a covered container or wrapped tightly. It keeps for 3–4 days in the refrigerator. For best texture, store slices rather than leaving the tart uncovered, since the custard can dry out and absorb refrigerator odors. Do not leave it at room temperature for longer than 2 hours.

To reheat, place slices on a baking sheet in a 325°F (165°C) oven for about 12–18 minutes, until hot throughout; leftovers should reach 165°F (74°C) when checked with a food thermometer. A microwave works for a quick portion, but can soften the crust: heat in short bursts and check that the center is thoroughly hot. The tart can be frozen, tightly wrapped, for up to 2 months, though the custard may turn slightly less smooth; thaw overnight in the refrigerator before reheating.

Frequently Asked Questions

What is Cheddar Gorge cheese?
Cheddar Gorge is in Somerset, England, a region associated with traditional cheddar-making and cave-aged cheeses. Cheese sold under a particular producer’s name can vary in age and sharpness, so check the label and adjust seasoning to suit. This recipe also works with a mature cheddar from another maker.

Can I make the tart ahead?
Yes. Bake it up to a day ahead, cool it, and refrigerate it covered. Reheat in a 325°F (165°C) oven until hot, or serve it cool or at room temperature after keeping it refrigerated until shortly before serving.

Can I use a different pan?
A 9-inch (23 cm) pie plate works well, though the sides may be higher and the tart may need a few extra minutes in the oven. Begin checking at 28 minutes and rely on the filling’s set appearance and 160°F (71°C) center temperature rather than the clock alone.

Why did my filling turn watery?
Excess liquid from undercooked onions or vegetables can loosen the custard. Cook onions until their moisture has mostly evaporated, and drain or squeeze moisture from additions such as spinach. Also avoid overbaking: a custard that is cooked too long can release liquid and become grainy.

How can I tell when the tart is done?
The edges should look set and lightly puffed, while the very center may tremble slightly when the pan is nudged. Confirm that the center reaches 160°F (71°C) with a food thermometer; the short resting time will help the filling finish settling.

Can I prepare the onions in advance?
Yes. Cook them up to 3 days ahead and keep them covered in the refrigerator. Bring them close to room temperature before assembling, or warm them briefly in a skillet so they do not chill the custard mixture and slow baking.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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