Caramelized Onion Tart

Onion tart in a pan with forks on table.

Caramelized Onion Tart is going to be your new favorite way to enjoy onions. I love onion rings, onions in fajitas, and of course onions in a pie crust. So, when Diamond Nuts asked me to create a savory pie with their Walnut Crust, I thought let’s use onions, haha!

This recipe combines the natural sweetness of caramelized onions with rich manchego cheese and crispy bacon, baked in a crispy walnut crust. Topped with shallots for a little color with added flavor. A simple filling that will satisfy your need for a warm savory breakfast on a cold morning.

Wood table with bowl of shallots, apron, and walnuts.
Diamond Nut pie crust filled with shallots and thyme leaves.

Let’s discuss some of the flavors of this tart, starting with the crust. Diamond of California offers a ready to use Walnut Pie Crust with a buttery crumbly texture. No artificial flavors or corn syrup makes this a perfect vessel for your savory pie. Plus walnuts, onions, and thyme are a fabulous flavor combo.

What do caramelized onions taste like? Well, by browning the sliced onions in olive oil it brings out their natural sweetness. To balance out the sweet flavor I added pieces of salty bacon, with manchego crumbles.

Manchego cheese is made from unpasteurized sheep’s milk. Originating from Spain, this crumbly full body cheese offers fruity, nutty, sweet, and tangy flavors. It’s a rich cheese that is just oh so delicious.

Onion tart on table with apron and bowl of shallots.

Tips for Caramelized Onion Tart

  • Use large yellow onions and cut into thin slices.
  • Caramelize onions until brown and fragrant. Olive oil can be swapped out for butter if desired.
  • If you add water to your onions while on the skillet, make sure to drain before transferring to cream.
  • Bake tart in the aluminum foil tray the crust comes in. To use a different pan for aesthetic purposes, simply freeze the pie crust for 2 hrs. Gently lift from aluminum foil tray and transfer to a pie dish of the same size. (If the pie dish is too big, the crust will crack). This is purely optional and not necessary.
  • Once the baked tart is cooled you can cover with aluminum foil and store in the fridge for 2-3 days, warming again before serving.
Close up of an onion tart in pie plate.
Slice of onion tart on a white plate.

Caramelized Onion Tart

Caramelized Onion Tart made with manchego cheese, yellow onion, bacon, and a walnut crust. Delicious savory tart recipe made with caramelized onions.

Course Breakfast, Main Course
Cuisine American
Keyword onion
Prep Time 30 minutes
Cook Time 30 minutes
Total Time 1 hour
Servings 8 slices


Tart Filling

  • 2 (570 grams) Large Yellow Onions peeled and thinly sliced
  • 3 Tbsp Olive Oil
  • 1 Tbsp Fresh Thyme Leaves extra sprigs for garnish
  • 1 Cup (250 ml) Heavy Cream
  • 2 Larg Eggs lightly beaten with a fork
  • 1/2 tsp Salt
  • 1/4 tsp Ground Pepper
  • 2/3 Cup ( 80 grams) Manchego Cheese crumbles, do not use rine
  • 1 Cup (225 grams) Bacon Pieces cooked and broken into pieces
  • 2 Shallots Sliced for topping


Make Onion Tart

  1. Cook bacon on medium skillet at medium heat until just before crispy. Transfer to paper towel lined tray to absorb excess grease.

  2. In a large skillet, combine sliced onions and olive oil. Cook on medium low heat for 10 minutes until onions are soft, occasionally stirring to prevent sticking to bottom of pan.

  3. Add the thyme leaves and continue cooking (and stirring when needed) until translucent brown. (10-15 min) Add a Tbsp of water as needed if sticky too much to pan. Set aside to cool.

  4. In a large bowl, stir together cream, eggs, salt, pepper, and manchego crumbles.

  5. Add caramelized onions to the cream mixture and softly fold together with spatula.

  6. Transfer 1/2 of the onion mixture to the Walnut Pie Crust. Sprinkle with pieces of bacon.

  7. Repeat with second half of filling.

  8. Top with sliced shallots. (option to slightly cook on skillet prior)

  9. Place tart (still in aluminum foil dish) on a cookie sheet onto middle oven rack.

  10. Bake at 375 F (190 C) for 30-35 minutes until golden brown.

  11. Place onion tart on cooling rack for 15 minutes before slicing and serving warm.

*This Recipe is Sponsored by Diamond of California All thoughts and text are my own. Thank you for supporting the companies that help make Two Cups Flour possible.

Slice of onion tart with a bite on a fork.
Diamond nut pie crust on table with bowl of shallots.

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