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Zucchini and Caramelized Onion Galette on parchment paper

Zucchini and Caramelized Onion Galette with Gruyere

Flaky, buttery and tender pastry enclose zucchini, caramelized onion, gruyere and spices in this rustic galette.
Prep Time 1 hour
Cook Time 1 hour 10 minutes
Total Time 2 hours 10 minutes
Servings 4 -6
Calories 820kcal
Author Traci York | Vanilla And Bean


For the Pastry:

  • 1 1/4 C White Whole Wheat Flour *See Note 6 3/4 oz
  • 1 1/4 C All Purpose Flour 6 1/4 oz
  • 1/2 tsp Sea Salt
  • 2, 8 oz Sticks of Butter cold
  • 1/2 C Milk
  • 1 Tbs Apple Cider Vinegar
  • 2 Tbs Water ice cold

For the Galette Filling:

  • 4 lbs Sweet Onions (about 4 smallish )
  • 3 lbs Zucchini (about 6 small)
  • 1 C Gruyere grated (8 oz)
  • 1 Tbs Olive Oil
  • 1 Tbs Butter
  • 2 tsp Sea Salt divided
  • 1 tsp Granulated Sugar
  • 1/4 tsp Ground Pepper
  • 1/8 tsp Red Pepper Flake dried, optional
  • 1/4 tsp Tarragon dried
  • 1/4 tsp Thyme dried
  • 3 Sprigs Thyme fresh for garnish
  • 1 Tbs Egg + 1 Water


For the Pastry**:

  • **Make one day ahead if time permits
  • Cut the butter, into 1/4" slices using a knife, or a bench scraper. Pop the butter in the freezer for 5 minutes while you prep the rest of the ingredients.
  • Measure out the milk and apple cider vinegar and mix together. Let set for 5 minutes to sour (this is your buttermilk).
  • Mix the flour and salt together in a large bowl. Get the cold butter out of the freezer and drop it into the flour/salt mixture. Use a pastry cutter or a fork to cut the butter into the flour. Stop working the butter into the dough when the butter pieces are about the size of almonds, or slightly smaller.
  • Make a well in the center of the bowl and add the milk mixture. Use your hands to mix the flour mixture with the milk mixture. Dump the mixture out on a floured surface when the mixture resembles a shaggy mass. Use a bench scraper to gather all the bits of flour together shaping it and pushing it together. Make a well in the center of the dough and add 2 Tbs of cold water. Use the bench scraper to start folding and pressing the dough over and on top of its self, working in the water. Work quickly so the dough stays cold. Fold it over on its self about 9-10 times shaping it into a circular mass as you go, using your hands as needed. Flatten it out using a rolling pin to about 1/2" making sure it is in a rounded shape. Wrap it securely in plastic wrap and refrigerate overnight or for at least two hours.

Zucchini Prep:

  • Grate the zucchini using a microplaner or box grater, reserving 1/2 of one zucchini. Cut the reserved zucchini into 1/8" slices to be arranged on top of the galette before baking. Set aside. Place the shredded zucchini in a colander over the sink and add 1 tsp of salt. Mix well. Let sit for 25 minutes.
  • Place zucchini, in 1 C batches, on a kitchen towel. Squeeze out the liquid and place the shredded zucchini in a large mixing bowl. Set aside.

For the Onions:

  • While the zucchini is draining, cut the onions in half and slice length wise cutting in thin 1/2 moon shapes. Melt the olive oil and butter in a large non stick sauté pan over medium-low heat. Place the onions in the pan with 1 tsp salt, and sugar. These will take about 30 minutes to caramelize. Stir occasionally.

Roll out the Dough:

  • Remove the pastry from the fridge. Have ready a sheet pan, plastic wrap, parchment paper, flour for dusting, a rolling pin and ruler.
  • Dust the work surface with about 1 Tbs of flour. Place the pastry on the work surface. Use the rolling pin to 'condition' the pastry by beating it down by about 1/4". Turn the pastry as you work it.
  • Flour the rolling pin and the top of the pastry to keep them from sticking to each other. Use the rolling pin to start rolling out the dough turning the dough 1/4 way around as you roll it out and the dough gets larger. Keep rolling, adding flour under and on top of the pastry as needed to keep the pastry from sticking. Work quickly, you want it to stay cold! If it's sticking too much, place the pastry on the parchment lined sheet pan and pop it in the fridge for 10 minutes. Roll the pastry out to 16" round. If there is a tear in the edge, tap your finger into a bit of water and seal up the tear.
  • Place plastic wrap completely around the pastry (if it is not covered well, it will dry out in the fridge!) Place the dough in the fridge to rest for at least 20 minutes; 30 is better! Preheat the oven to 400F.

For Zucchini/Onion Mixture:

  • In the large mixing bowl with the zucchini, add the caramelized onions, ground pepper, red pepper flakes, tarragon, dried thyme and gruyere. Mix well and taste for adjustment in seasoning. Adjust if needed.

To Assemble the Galette:

  • Mix the egg and 1 Tbs of water well. Have a pastry brush ready.
  • Assemble the galette on a parchment lined sheet pan. Spoon the zucchini mixture in the center of the pastry leaving at least 2" of crust on the edges. Begin folding the pastry inward, over the zucchini mixture. The pastry will overlap all the way around.
  • Lay the 1/8" cut zucchini in a decorative overlapping circle on the open part of the galette.
  • Brush the egg/water mixture over the pastry.
  • Bake the galette for 45 minutes on the center rack, turning 1/2 way through the bake time.
  • Let rest for 5 minutes, then cut using a pizza cutter.
  • Garnish with fresh thyme leaves and flowers (if available).


*All purpose flour can be used instead of white whole wheat flour. Use 2 1/2 C (13 1/4 oz) of All purpose flour and omit the white whole wheat flour.
**Making this pastry one day before you need it allows the dough to rest longer and yields a more pliable pastry to work with.
This galette serves 4-6 as a main or up to 16 as an appetizer.
The prep and cook time does not include the time it takes for the dough to rest.
Recipe adapted from The Smitten Kitchen Cookbook.


Calories: 820kcal | Carbohydrates: 103g | Protein: 27g | Fat: 36g | Saturated Fat: 19g | Cholesterol: 100mg | Sodium: 1823mg | Potassium: 1537mg | Fiber: 12g | Sugar: 33g | Vitamin A: 1652IU | Vitamin C: 84mg | Calcium: 517mg | Iron: 5mg