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About This Onion Tart Recipe
This recipe was born as a version of peach upside down cake. I initially tweaked it to make a summer heirloom tomato cake with fresh herbs and a savory tasting batter. After thoroughly enjoying several versions of it, the idea to use sweet onions entered my head and I developed the onion tart recipe below.
You can call the glorious baked disc that results onion tart, upside down onion cake or even onion pie. Below I demonstrate it using milk stout in the batter because I love the resulting flavors, deep color and texture but you can use a variety of different liquids to whip up a batter of similar consistency.
Besides beer I have used buttermilk, kefir, yogurt thinned out with water to the consistency of buttermilk, plain soda water, beef or vegetable broth, heavy cream and whole milk. They all work well.
The resulting textures and flavors vary slightly from each other depending on the liquid used, but because all other ingredients remain the same and there is extra virgin olive oil added, the batter is always flavorful and forms a nice moist crumb similar (but superior) to that of butter swim biscuits.
Baking Dish Recommendation
When selecting a dish to bake your onion tart make sure that it is 10 inches in diameter, has a non-stick surface and is nicely curved along the bottom as it transitions up into the vertical periphery. A heavy bottomed pan or skillet such as cast iron skillet or a small enamelled cast iron braiser (about 2.25 quart in volume) such as I use below is perfect.
With the right baking dish the tart will not only flip over easily at the end, once it has cooled down some, but the onions will caramelize really well and the batter will bake evenly.
Ingredients
Onions. You can use whatever onions you'd like. Yellow onions have a stronger aromatic flavor, while sweet onions are much milder.
Butter and olive oil. Both are used to cook the onions in - the butter for flavor and olive oil so that the butter does not burn and for more flavor. (More olive oil goes in the batter to keep the tart moist).
Thyme and seasonings. Fresh thyme (leaves picked) cooks together with the onions, and is also used for garnish when the onion pie is served. Kosher salt and black pepper to season to onions.
Dry ingredients. All-purpose flour (or a gluten-free baking equivalent), baking powder, sugar (white, granulated), onion powder (for another dimension of the aromatic), kosher salt and dried thyme.
Liquid. Stout, porter ale and most beers that are not too bitter and have biscuity, bready notes and pronouced malty sweetness are welcome here. Buttermilk, kefir and thinned out yogurt (with water, to buttermilk consistency) work equally well, just a bit more of them is needed. Milk, heavy cream and beef broth also do the job of binding the batter ingredients.
Olive oil. Use extra virgin olive oil if you can to add to the batter. It rounds off the flavor and keeps the baked tart moist and delectable.
Workflow: Step-by-Step How to Make Onion Tart
All the steps involved are very simple and you just need to follow the sequence I have laid out below to organize your workflow. You can also watch the video within the Recipe Card for a coherent overview of the process.
The first stage of making this onion tart is to cook and soften the onions. The second stage involves preparing the batter and adding it to the partially cooked onions - in the second round in the oven the onions caramelize and the batter cooks through, soaking up the excess butter. Finally, you allow the onion tart to slightly cool down - mostly so that you can safely handle the baking dish and flip it over onto a plate to serve it.
- Begin by preheating the oven to 450 Fahrenheit. Melt the butter with the olive oil over a medium heat stove. Once melted, move it over a board near where you are working on the onions. Slice the onions thinly and begin creating the onion layer.
- Sprinkle the fresh thyme leaves over the melted butter at the bottom of the dish, then cover the entire bottom with a consistent layer of sliced onions. Not too thick, not too thin, keeping in mind that the onions will loose most of their volume as they cook.
- Season with salt and pepper to taste and place the onions in the oven for 15 minutes to cook through.
- While the onions are in the oven mix the batter. Whisk all the dry ingredients together, make a small well in the middle of the bowl and work in the stout or other liquid of your choice, then add the olive oil. Do not overmix, you do not need to develop the gluten proteins for this batter.
NOTE: The batter needs to be thickish, but slightly thinner than the batter for beer bread. Adjust ingredients as necessary if yours turns out too thick (like for biscuits) or too thin (like pancake batter).
Remove the baking dish with the onions from the oven and pour the batter over it. Use two spatulas to slightly adjust it and stretch it out to the sides, creating an even circle layer over the onions. There should be melted butter pooling around the periphery.
Bake for another 15 to 16 minutes, check to see if the batter has baked well or if it needs another two or three minutes.
When satisfied with the baked finish remove the onion tart from the oven and gently run a thin silicone spatula or similar around the circumference to separate the edges (most likely not needed, but will be useful if the coating was not perfectly non-stick.)
Allow a couple of minutes for the baking dish to cool down so you can comfortably handle it with kitchen gloves. Place a suitably sized flat plate on top. Holding the sides and pressing the plate down with your thumbs flip the onion tart.
Serving Ideas for Onion Tart
This baked onion goodness is most delicious while still warm. (You can also serve it at room temperature, even chilled). You can sprinkle it with feta or goat cheese crumbs or drizzle with balsamic reduction.
Slice with the sharp side of a pastry server or a slicing knife. Once plated you can garnish each slice with thyme and a drizzle of olive oil.
Enjoy the onion tart as an appetizer or offer it as a festive side dish to roasts, especially beef.
It is delightful as a light entree, with a side salad, and is an excellent option for a vegetarian main.
If you make it for Sunday brunch, serve it alongside two fried eggs and some bacon and enjoy!!
Storage and Reheating
Store leftover onion tart in an airtight container in the refrigerator.
To reheat you can use the microwave (expect reheated pizza slice quality:) or place it into a small baking dish and place it inside a 325 F oven just until warmed through.
You Might Enjoy
Baked Onions with Balsamic | German Onion Pie | Picanha Roast
Recipe
Onion Tart
Ingredients
FOR ONION TOPPING
- ½ stick butter 4 tbsp
- 1 tablespoon olive oil
- 2 medium onions
- 1 tablespoon thyme leaves picked fresh
- kosher salt to taste
- black pepper to taste
FOR BATTER
- 1 ¼ cup all-purpose flour
- ½ tablespoon baking powder
- 1 teaspoon onion powder
- 1 teaspoon salt
- 1 teaspoon dried thyme
- 1 teaspoon sugar
- 2 tablespoon olive oil plus a drizzle
- 1 cup milk stout or substitute*
Instructions
- In the baking dish add the 4 tbsps butter and 1 tablespoon olive oil and heat over medium heat stove until the butter melts. Remove the dish and set aside. Pre-heat the oven to 450 F.
- Thinly slice the onions. Sprinkle the fresh thyme leaves over the butter and oil mixture. Layer the thinly sliced onions, gently pushing them out towards the curved parameters of the baking dish. Season with kosher salt and pepper and place in the oven for 15 minutes.**
- In a bowl whisk together the flour, baking powder, salt, onion powder, dried thyme and sugar. Make a well in the middle and add the stout (or other liquid), then the olive oil and gently work them in the dry ingredients without over-mixing. The batter should be thickish, like muffins batter. (Thicker than pancake batter but thinner than biscuits batter).
- When the 15 minutes are up, take out the dish with the onions from the oven. Pour the batter over the onions and with the help of two silicone spatulas or similar stretch it towards the sides, forming an even layer, surrounded by a bit of pooling melted butter. Drizzle a bit of olive oil over the batter.
- Return the baking dish to the oven and bake for 15 minutes. Check the batter with a toothpick and decide if you need to leave in for extra 2-3 minutes. (Most likely the onion tart is done).
- Allow the onion tart to cool down a bit, slide a thin spatula along the periphery to make sure batter is not sticking to the sides. When the baking dish is safe to handle, using kitchen gloves, place a suitably sized plate over it. Pressing the plate down with your thumbs flip the baking dish over so that the onion tart is now onto the plate with the caramelized onions side facing up.
- Slice and serve. Garnish with your choice of fresh thyme leaves, feta cheese or goat cheese crumbles, drizzle of balsamic reduction or extra virgin olive oil.
Video
Brian
Amazing!! Fair amount of effort but the result was worth it 100%.
Milena Perrine
Glad to hear it worked out! Thank you, Brian for the feedback.