This air fryer onion tart is pure autumn comfort food: a flaky, golden pastry crust filled with slowly caramelized onions, crispy bacon and a silky egg and cream custard, finished with fresh thyme and a hint of nutmeg. It is rich, savory and slightly sweet from the onions, and it bakes beautifully in a small pan in your air fryer.

It is also the most-watched video on the Airfryworld Facebook page so far, so we turned it into a full recipe with exact amounts, timings and tips for a crisp, never soggy crust.

Air Fryer Onion Tart with Bacon and Thyme

Recipe by JuliaCourse: Appetizer, LunchCuisine: German, FrenchDifficulty: Easy

Servings

servings

Prep time

minutes

Cooking time

hour

Calories

465

kcal

Protein

Carbohydrates

Fat

Fiber

Total time

hour

minutes

A golden air fryer onion tart with flaky pastry, sweet caramelized onions, crispy bacon and a creamy egg custard flavored with thyme and nutmeg. Inspired by the classic German Zwiebelkuchen.

Ingredients

1 sheet puff pastry or shortcrust pastry, thawed
3 large onions, thinly sliced
150 g (5 oz) bacon bits or diced smoked ham
1 tablespoon butter
2 large eggs
1/2 cup heavy cream or crème fraîche
1/2 cup grated cheese, such as Gruyère or Emmental (optional)
1 teaspoon fresh thyme leaves, plus extra for garnish
1 pinch ground nutmeg
Salt and black pepper, to taste

Directions

Crisp the bacon
Cook the bacon in a large skillet over medium heat for 5 to 6 minutes until crisp. Remove it with a slotted spoon and leave about 1 tablespoon of the fat in the pan.
Caramelize the onions
Add the butter, the onions and a pinch of salt to the pan. Cook over medium-low heat for 20 to 25 minutes, stirring now and then, until the onions are soft, sweet and golden. Stir in the thyme and let them cool slightly.
Line the pan
Press the pastry into a 7-inch (18 cm) tart or cake pan that fits in your air fryer basket, trim the edges and prick the base all over with a fork.
Pre-bake the crust
Air fry the empty crust at 350°F (175°C) for 8 minutes until lightly golden. If the base puffs up, gently press it down with the back of a spoon.
Make the custard
Whisk the eggs with the cream, nutmeg, black pepper, a pinch of salt and half of the cheese.
Fill the tart
Spread the onions and bacon over the crust, pour over the custard and sprinkle with the remaining cheese.
Air fry the tart
Air fry at 320°F (160°C) for 20 to 25 minutes, until the custard is set with only a slight wobble in the center and the top is golden. Cover the edges with foil if they brown too quickly.
Rest and serve
Let the tart rest for 10 minutes before slicing. Garnish with fresh thyme and serve warm or at room temperature.

Notes

Yellow or sweet onions caramelize best. Red onions work too and give a slightly fruity flavor.
Let the onions cool a little before adding the custard, otherwise the eggs can start to set too early.
The tart keeps in the fridge for up to 3 days and tastes great cold.
For a vegetarian version, leave out the bacon and add sautéed mushrooms.

Julia’s Tip: Give the onions the full 20 minutes in the pan. Slowly cooked onions turn sweet and jammy, and that is where almost all the flavor of this tart comes from.

A Classic Inspired by German Zwiebelkuchen

Onion tarts are loved all over Europe. In France you will find tarte à l’oignon from Alsace, and in Germany, Zwiebelkuchen is a true autumn tradition. It is usually served warm in September and October, often with Federweisser, a young, slightly sparkling new wine that is only available during the grape harvest. The German version is traditionally made with a yeast dough baked on a large tray. This air fryer onion tart keeps the same comforting flavors of onion, bacon and cream, but uses ready-made pastry and a small pan, so it is quick enough for a weeknight.

How to Caramelize Onions for an Onion Tart

Slice the onions thinly and evenly so they cook at the same speed.
Use a wide pan and medium-low heat. High heat burns the edges before the onions soften.
Add a pinch of salt at the start. It draws out moisture and helps the onions break down.
Stir every few minutes and add a splash of water if they start to stick.
They are ready when they are soft, light golden and smell sweet, after about 20 to 25 minutes.

Puff Pastry or Shortcrust for an Air Fryer Onion Tart?

Both work well. Puff pastry gives a light, flaky crust with crisp, airy layers, just like in the photos. Shortcrust pastry is firmer and more buttery, and it holds a deep filling a little better, which makes it closer to a classic quiche. Whichever you choose, pre-baking the empty crust for a few minutes is the key to avoiding a soft bottom.

Slice of onion tart showing flaky pastry and a creamy custard filling with caramelized onions and bacon — A slice of onion tart with caramelized onions and bacon in a creamy custard.

Which Pan Fits in the Air Fryer?

A 7-inch (18 cm) tart pan with a removable base is ideal for most 5 to 6 quart basket air fryers. A round cake pan of the same size works too. For smaller air fryers, use a 6-inch pan and reduce the filling slightly, or make two smaller tarts one after the other. Leave a little space around the pan so the hot air can circulate.

How to Tell When Your Air Fryer Onion Tart Is Done

The custard should be set around the edges with only a slight wobble in the very center when you gently shake the pan. A knife inserted halfway between the center and the edge should come out clean. The tart keeps cooking from its own heat while it rests, so it firms up completely after 10 minutes.

What to Serve with Onion Tart

A crisp green salad with a mustard vinaigrette
A bowl of pumpkin or tomato soup
Pickles and a few slices of good cheese for a rustic lunch
A glass of dry white wine, or Federweisser in autumn

Storage and Reheating

Keep leftover air fryer onion tart covered in the fridge for up to 3 days. It is delicious cold for lunch, or reheated in the air fryer at 300°F (150°C) for 5 to 6 minutes, which keeps the pastry crisp. You can also freeze individual slices for up to 2 months and reheat them from frozen.

Frequently Asked Questions

Can I make an air fryer onion tart without bacon?

Yes. Leave out the bacon and add sautéed mushrooms, a little smoked paprika or extra cheese for a vegetarian version full of flavor.

Can I prepare it ahead?

Yes. Caramelize the onions and cook the bacon up to 2 days ahead and keep them in the fridge. Assemble and bake the tart on the day.

Why is my tart watery?

The onions were probably not cooked long enough and released liquid during baking. Cook them until all the moisture has evaporated and they look glossy and golden.