Gluten-Free Caramelized Onion and Brown Butter Tart by Chef Lizette Marx, Holistic Chef Instructor at Bauman College

Caramelized Onion and Brown Butter Tart by Chef Lizette Marx, Holistic Chef Instructor at Bauman College

Caramelized Onion and Brown Butter Tart by Chef Lizette Marx, Holistic Chef Instructor at Bauman College

Chef Lizette Marx

Chef Lizette Marx

Chef Lizette Marx, Holistic Chef Instructor for Bauman College’s Holistic Chef Online Culinary Program shares a delicious Gluten-Free Caramelized Onion and Brown Butter Tart recipe.

I love how the simple act of caramelizing onions creates such an amazing foundational flavor. Start cooking onions low and slow and the mouth-watering scent of them will immediately peak your appetite. My version is a little lighter and the crust is gluten-free.

The choice to make the crust gluten-free is more than just serving up a version for those who must live without but also because I think if you can do it and there is virtually little difference then why not? A recipe without all-purpose flour is a triumph in my book. It is more interesting in flavor and I love the challenge of taking a traditional recipe and making it less inflammatory and perhaps a little healthier.

My crust contains a combination of brown rice, almond and cassava flours. The original recipe also uses Gruyere cheese. I love that idea and you can certainly add it to this recipe but I chose to omit it so the onions could take their rightful place as the star of the show.

Find out more about Chef Lizette by visiting our Faculty Page

Caramelized Onion and Brown Butter Tart



  • 1 cup cassava flour
  • 1/4 cup almond flour
  • 1/4 cup brown rice flour
  • 2 tablespoons arrowroot flour
  • 1/4 teaspoon sea salt
  • 2 teaspoons palm sugar (optional)
  • 6 tablespoons very cold butter, cut into cubes
  • 1 egg
  • 1 tablespoons apple cider vinegar
  • 1 tablespoon ice water


  1. Using a food processor with the “S” blade or a large bowl, pulse or whisk together flours with sea salt and palm sugar.
  2. Add butter and work in with a pastry cutter, fork or if using a food processor pulse until butter and flour resemble coarse crumbs.
  3. Mix in egg and apple cider vinegar. Dough will begin to come together and form a ball. If the ball of dough crumbles easily, add a little ice water. Once dough ball stays together without being sticky it is ready to shape into a ball.
  4. Using a bench scraper or butter knife cut dough ball in half and shape each half into a disk and cover with parchment paper or plastic wrap. Chill in the refrigerator for 30 minutes.
  5. Turn chilled dough onto a large piece of parchment paper on your counter and cover with another sheet of parchment paper or a large sheet of plastic wrap. Flatten dough into a disc and beginning rolling out to 1/4” thick round. Don’t worry if you aren’t able to roll out dough into a circle, just make it big enough to cover the bottom and sides of a 9”-inch tart or pie pan.
  6. To transfer rolled out dough into the tart pan, carefully peel off the top layer of parchment or plastic wrap. Place tart shell face down onto dough then slide your hand under the bottom layer of parchment and place your other hand on the bottom of the tart shell and quickly turn everything over so the dough nestles onto the bottom of the pan. It is quite normal for your dough to crack or break apart a little at this point. Don’t panic…just take a smooth inhale and long exhale. This is where we recall the many hours of fun we used to have playing with play dough and start pressing the dough firmly into the tart shell by hand until it lines the bottom and sides of the pan as evenly as possible.
  7. Your warm hands will have warmed up the crust so now it’s time to chill the dough in a freezer for about 30 minutes or so. Cover with plastic wrap and chill. While the dough is chilling, preheat your oven to 425 F and then start making the filling.


  • 4 to 5 medium sized onions, sliced thinly (about 7 cups)
  • 4 garlic cloves, minced
  • 2 tablespoons olive oil
  • Couple pinches of sea salt
  • 1 teaspoon dried thyme
  • 1/2 teaspoon sea salt
  • 1/8 teaspoon white pepper
  • 2 tablespoons butter, melted until lightly browned
  • 2 tablespoons cassava flour
  • 1/2 cup whole, organic milk, warmed (for dairy free choose either almond, cashew or coconut milk)


  1. Slice onions thinly by removing the outer layers and making a shallow cut on the stem end to prevent the onion from rolling. Place cut side down and cut in half from the root end down. Lay each half cut side down and slice thinly along the “pin-strip” marking to make thin slices.
  2. Heat a large sauté pan or even a soup pot on medium low heat and add olive oil.
  3. Swirl oil evenly along bottom of pan and add all of the onions, spreading out evenly. Cover and lower heat and allow onions to sweat for about 5 minutes. Remove lid and add a couple pinches of sea salt and the minced garlic. Stir and cover again to sweat the onions  with the garlic for another 5 to 8 minutes.
  4. Remove cover and stir in thyme and 1/4 teaspoon or so of sea salt (honestly I never measure here so another pinch or two of sea salt will work). Allow the onions to cook uncovered until they become uniformly light caramel in color and very soft. Stir once in a while to prevent sticking. This will take about 30 to 40 minutes on low heat. Low and slow is the way you want to go so don’t rush this magical process because the resulting flavor is heavenly.
  5. While onions are caramelized over low heat, make brown butter. Melt 2 tablespoons of butter over low heat in a small saucepan. Continue cooking until melted butter starts to brown. Remove from heat and allow to sit for a few minutes. Then stir into the onions. Voila caramelized onions with brown  butter!
  6. Once onions are caramelized, sprinkle in cassava flour and stir thoroughly into onions and gently cook the flour. Allow pan to become dry but don’t let onions scorch so watch your heat.
  7. Once flour is lightly toasted, turn off the heat and slowly pour in warm milk. At this point stir well with a wooden spoon. Remove pan from burner and allow filling to cool.
  8. While filling is cooling pre-bake tart crust.
  9. Remove chilled crust from freezer and poke holes into the bottom of the crust with the tines of a fork.
  10. Bake in a 425 F oven for about 8 to 10 minutes or until crust is lightly browned. Remove tart shell and allow to cool. While cooling, reduce oven temperature to 350 F.
  11. The final step!
  12. Scoop caramelized onion filling into pre-baked tart shell and bake for 15 to 20 minutes. (Don’t forget to reduce the temperature to 350 F! If you do forget your onions will be browner which is actually okay but the risk is the crust might get too toasty.)
  13. When the tart comes out of the oven it will be piping hot and difficult to cut. It will also smell divine so you’ll want to start eating it right away. If you do, prepare for your slices to be a little messy and goopy. If you want neater pieces allow tart to cool for about 15 minutes.


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