Caramelised Onion Tart

This recipe for Caramelised Onion Tart is based on a recipe in Vegetarian Kitchen by Sarah Brown. I bought this book many years ago, in my early twenties, when I was a vegetarian. Subsequently, I have changed my diet to include fish and some meat, but I still love vegetarian food and often cook meat-free at home.

I have cooked this recipe many, many times. It is, in my opinion, simply the best onion tart ever. Occasionally, I will think that I will try a different recipe but I always come back to this one. The key to its luscious loveliness is to cook the onions really, really slowly for a long, long time so that they soften and gently caramelise without burning.

Nutmeg

The taste of the caramelised onions is enhanced by the nutmeg, a spice that has a myriad of uses in both sweet and savoury dishes. It is really worth buying whole nutmegs and grating a bit off them when you need it rather than buying ground nutmeg. Just use an ordinary grater, there is no need to buy a special nutmeg grinder. The pungency of fresh nutmeg is a revelation and adds an extra dimension of flavour to the tart.

Caramelised onion tart, onion quiche, caramelised onion quiche — Pastry case for tart

Equipment

Large, heavy frying pan, quiche or flan dish (28 cm)

Caramelised Onion Tart

★★★★★ 5 from 1 reviews

Author: Tastebotanical
Prep Time: 15
Cook Time: 55
Total Time: 1 hour 10 minutes
Yield: 1 tart serving 8 people 1x
Category: Tart
Method: Baking
Cuisine: English

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Description

This luscious tart is filled with caramelised onions, subtly flavoured with nutmeg, set in a rich cheese custard. It is fantastic for hot, warm or cold which makes it very versatile. I honestly believe this is the best onion tart!

Ingredients

Scale

For the pastry:

275 g plain flour
125 g fat (I use a mix of half butter and half Trex as I think this makes the lightest pastry)
Salt
A little water

For the filling:

6 large onions (white or red is fine) plus a further 3-5 onions or shallots for decoration
40 g butter and 1 tbs oil
Salt and pepper
1 tsp brown sugar (optional)
Grated nutmeg (best to grate this from a whole nutmeg as this has best flavour)
100 ml double cream
2 eggs
100 g strong cheddar cheese (grated)
A little olive oil

Instructions

Set your oven to 180 C, 350 F or Gas Mark 4.
Make the pastry. Put the flour in a bowl. Add the fat and combine – either by “rubbing in” by hand or processing – until the mixture resembles breadcrumbs. Season with salt and pepper. Add a little cold water (2-3 tbsp) and shape the mixture into a dough.
Peel and chop the onions.
Heat the butter and oil in your frying pan. It helps if the pan is good quality with a thick bottom as this will disseminate the heat evenly and prevent burning.
Add the onions to the pan, season with salt and pepper, and cook at a very low heat for about 30 minutes. Keep an eye on them to make sure they are not burning and stir occasionally. The onions are done when they are light brown, soft and, when tasted, are sweet.
Season the onions with the grated nutmeg to taste (about half a tsp – although I add a bit more as I like it!). You can add a tsp of brown sugar to increase the sweetness of the onions at this stage if you wish.
Set the onion mixture aside to cool slightly.
Roll out your pastry and use it to line your quiche or flan dish. Bake for 5 minutes in the oven to allow the pastry to “set”. This will stop the filling making it soggy!
Crack the eggs into a mixing bowl, add the cream, and beat until combined. Finely grate the cheddar cheese and add to the mixture.
Now place the onion mixture in your pastry case. Pour the egg mixture over it.
Thinly slice the onions or shallots that you have set aside for decoration. The aim is to have a number of different sized circles of onion or shallot which you can use to decorate the top of the tart. Arrange artistically (!) and then brush with a little olive oil and season with salt and pepper.
Place your quiche or flan dish in the oven and cook for 25 minutes.
The tart can be eaten hot, room temperature or cold.

Keywords: onion, tart

Love this recipe? You may also like

Butternut Squash Tart with Chilli and Sage

Herb Tartlets

Butternut Squash Tart with Chilli and Sage

My Butternut Squash Tart with Chilli and Sage is a great summer tart which can be served either hot or cold. I came up with the idea for this recipe as an alternative to the Caramelised Onion Tart that is a regular family supper. I wanted to do something that had a similar sweetness but which was also a bit different.

The resulting tart uses butternut squash, which is slow-cooked to enhance its natural sweetness, and then gives it a bit of extra zing with the addition of chilli and sage. Both are good companions to squash – the chilli cuts through the sweetness and the sage gives it a savoury depth of flavour. Don’t be alarmed by the chilli. The amount involved is relatively small but really does pep up the tart. My children have varying views on chilli (ranging from “Carolina Reaper for breakfast, please” to “Yeeeuch”) but they all like this tart.

I like to serve this tart with my Red Slaw – to keep the bright colour thing going! They taste good together – the fresh crunchiness of the slaw goes well with the sweet-savoury tart – and they also look pretty!

What you need to know about this recipe

I generally make my own pastry. I was a late learner when it came to pastry and for years used ready-made versions. However, a few years ago I decided I had to get to grips with pastry-making and discovered how easy it is. So, if you have the time to make your own pastry, it is really worth doing as the taste will be much better than anything you can buy in the shops. However, if you don’t have the time or inclination, you can make this recipe using ready-made pastry and it will still taste pretty good.
Whether you are making your own pastry or using ready-made, it is really important to bake the empty pastry case in the oven for 15 minutes before you add the filling (step 7). This sets the pastry and means that it is properly cooked so it will be crisp and delicious rather than soft and soggy.
Cooking the onions and cubed squash on a low heat for 30 minutes until they become caramelised (step 5) is a crucial part of this recipe. You need them to be soft in texture and with the rich sweetness that comes from slow cooking.
If you don’t like chilli, you can leave it out. However, it is fairly mild and does give a good balance to the sweetness of the caramelised squash and onions.
I add sage as I think it goes particularly well with butternut squash. I think fresh sage is preferable. However, if you do not have it to hand, you can use dried sage. If you do not have any sage, or do not like it, you can substitute other herbs. I think thyme, oregano and rosemary would all be good in this recipe.

Other butternut squash and pumpkin recipes

If you like the earthy sweetness of butternut squash and pumpkin, you might like some of my other recipes.

Butternut Squash Hummus is a twist on traditional hummus which has the added sweetness of roasted squash
Butternut Squash Soup with Peanut Butter is a vegan savoury soup which combines the sweet squash with deliciously nutty peanut butter
Pumpkin and Sweetcorn Soup combines two traditional flavour partners in a hearty vegetarian soup
Filo Triangles with Roasted Butternut Squash, Chilli and Pinenut filling are a brilliant lunch, picnic or snack recipe

Other quiche and tart recipes

Savoury tarts and quiches are a fantastic, cook-ahead simple supper or lunch. They are easy to make and are great either hot or at room temperature. They can also be easily divided into portions if you are feeding a large number of people. Easily transportable, they also make a good addition to lunch-boxes or basis for a picnic. Here are some of my favourites.

Asparagus Quiche is a simple quiche-style savoury tart that highlights the taste of fresh asparagus. I also have a very simple Asparagus and Herb Cheese Tart which uses ready-made puff pastry.
Two kinds of onion tart – Caramelised Onion Tart which is based on sweet, slow-cooked onions and another version, Onion Tart with Wild Garlic, which has the addition of fresh herbs. I also have an easy Shallot Tart with Thyme and Anchovy which uses ready-made puff pastry.
My Garlic Tart is a garlic-lovers delight and uses three bulbs – yes, bulbs not cloves – of garlic
I also have two very different carrot-based tarts. Carrot and Coriander Tart combines these two classic flavours in a simple quiche-style savoury tart. Carrot Tart uses ready-made puff pastry and combines large pieces of carrot with orange and soft cheese.
Beetroot Tart is deliciously sweet and earthy. My Tomato Tart is also sweet but has is lighter and fresher.
Spinach Tart combines leaf green spinach with feta and crunchy pine-nuts.
Feta Quiche with Roasted Peppers is a fantastic comination of rich, smoky roasted peppers with salty feta cheese.
I also have a couple of fish-based recipes. My Crab and Prawn Tart has Asian-inspired flavours of coriander, lime and chilli. My Smoked Salmon Tart with Prawns is easy to make and is perfect for a celebratory meal or party.
In addition to larger quiches and tarts, I also have a recipe for individual Herb Tartlets which are great as canapes or snacks.

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Recipe for Butternut Squash Tart with Chilli and Sage