FrenchMedium · Warm
Tarte aux Oignons Caramélisés et Pommes
A comforting French-style tart featuring sweet caramelized onions and tender apple slices nestled in a tender oat flour crust. This allergen-conscious version proves that free-from baking can be just as indulgent as the classic.
Prep
20 min
Cook
40 min
Rest
10 min
Total
1h 10m
Method
Prepare the Tart Crust
1
In a large mixing bowl, combine oat flour, salt, sunflower oil, and cold water. Mix with a fork until a cohesive dough forms.
2
Prick the crust several times with a fork. Place a piece of parchment paper over the crust and add pie weights or dried beans. Blind bake for 12 minutes until lightly golden.
Prepare the Caramelized Onions and Apples
4
Cook the onions, stirring occasionally, for 30-45 minutes on low heat (around 300°F) until they are deeply golden, jammy, and caramelized. Add the white sugar and salt, stirring to combine, then cook 5 more minutes.
5
Remove from heat and set aside. The mixture should be jammy and fragrant.
6
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Assemble and Bake the Tart
7
Remove from oven and allow to cool for at least 10 minutes before slicing. Serve warm or at room temperature.
B
Nutri-Score
Good balance
A–E · lower is better · score 1
Calories
779
per serving
Calorie-dense · 779 kcalSource of fibre · 9g
Protein
16g
Carbs
103g
Fat
36g
Sat. fat
5g
Fiber
9g
Sugar
35g
Sodium
770mg
Gluten FreeDairy FreeEgg FreeNut FreeSoy FreeVeganRefined Sugar ConsciousHeart HealthDigestive WellnessGluten SensitivityFiber ConsciousWhole Grain
Nutri-Score is a general nutritional-balance guide, not medical or dietary advice.
A
Environmental impact
Very low impact
A–E · lower is better · includes estimates
kg CO2e
0.3
per serving
ACarbonAEU all-round· both agree
Water
0.3m³
Land
25Pt
Runoff
0.07g P
Oat Flour drives 26% of this recipe’s estimated footprint.
Carbon from Poore & Nemecek 2018; water, land & runoff from Agribalyse — modelled averages for comparing recipes, not a measurement of your groceries.
Flavor Profile
5
Umami
7
Sweet
4
Salty
2
Sour
1
Bitter
0
Spicy
Textures
TenderSilkyCrispChewySoft
Aromas
SweetCaramelizedFruityVanillaCitrus
Kitchen Equipment
Techniques
Safety & Storage
Cross Contamination
Use certified gluten-free oat flour to avoid wheat cross-contamination; store separately from wheat flours and clean all surfaces and utensils thoroughly before use
Allergen Warning
Verify maple syrup label for sulfite content if serving to individuals with sulfite sensitivity; many commercial brands add sulfites as preservatives
Cooking Temperature
Blind bake tart crust at approximately 375°F; ensure oven is preheated and use pie weights to prevent uneven baking or crust bubbling
Handling
Handle hot tart crust with care when removing parchment and weights; use protective gloves to prevent burns
Storage
Refrigerate leftover tart promptly; the sweet custard filling contains no preservatives and should be consumed within 2-3 days
Shelf Life
Best consumed within 2-3 days when refrigerated; discard if left at room temperature for more than 2 hours due to perishable filling
High Risk Population
This recipe avoids milk, eggs, peanuts, tree nuts, soy, fish, and shellfish; however, verify all individual ingredient labels for hidden allergens and cross-contact risks for highly sensitive individuals
Equipment Safety
Clean stand mixer or utensils thoroughly between uses if also preparing allergen-containing recipes to prevent cross-contact
Pro Tips
Technique
When caramelizing onions, don't rush the process—low and slow is the secret to achieving that deep golden sweetness. I set my timer for 15 minutes and resist stirring too often, letting the natural sugars develop into that jammy, fragrant texture that makes this tart special.
Substitution
If oat flour isn't available, you can substitute with a gluten-free flour blend, but make sure it's a 1:1 baking blend designed for pies. I've tested almond flour too, though it changes the texture to be denser—still delicious, but different from the original intent.
Equipment
A 9-inch tart pan with a removable bottom works beautifully here, but a standard pie dish works just fine too. The key is ensuring your crust holds its shape when you remove the tart from the pan for serving.
From the chef
When my daughter first tried a traditional French onion tart, I knew I had to create a version she could enjoy safely without feeling like she was missing out. This tart has become our weekend comfort food—the sweet caramelized onions and tender apple slices in that buttery oat flour crust prove that allergen-free baking can be just as indulgent as the original. Every bite reminds me why I never compromise on flavor, even when cooking for the most restricted diets.
TagsFrenchTartGluten FreeAllergen ConsciousCaramelized OnionAppleOat FlourSweet Custard
AllergensGlutenSulfites
Source: generated · June 10, 2026