Quick Takeaway
These lemon squares are a low oxalate dessert with a buttery shortbread crust made from rice flour and cornstarch, topped with a tangy lemon custard sweetened with honey. No wheat flour and no almond flour. New here? Start with our Low Oxalate Foods List.
These low oxalate gluten-free lemon squares have a crisp, buttery shortbread crust and a tangy lemon filling sweetened with honey. If you love classic gluten-free lemon bars, this version uses rice flour and cornstarch in the crust instead of wheat flour or almond flour. Use certified gluten-free oat flour in the filling, and let the baked squares cool on the counter for 20 minutes before cutting.
Why You’ll Love This Recipe
- Naturally gluten-free. Rice flour and cornstarch make the crust, and a little oat flour helps the custard set. All three are on the low-oxalate flours list.
- No refined sugar. Honey sweetens the lemon layer and granulated monk fruit sweetens the crust.
- Bright lemon flavor. A full third of a cup of lemon juice gives the filling a real tang.
- Simple to make. One bowl for the crust, one bowl for the filling, and no mixer needed.
- Naturally low oxalate. Every ingredient is low oxalate, so you can enjoy a classic bakery dessert without the almond flour.
Why Rice Flour and Cornstarch
Most lemon bar recipes use wheat flour or almond flour for the crust, and both are high in oxalates. White rice flour and cornstarch are two of the best low-oxalate swaps. Rice flour gives the crust structure, and cornstarch keeps it tender and crisp, so it bakes up just like a classic shortbread. In the lemon layer, a small amount of oat flour and cornstarch help the eggs set into a firm custard that slices cleanly.
Wondering if an ingredient is low oxalate? Check any food in seconds with our free Food Look-Up tool.
Ingredient Notes
- Rice flour and cornstarch. Both low oxalate. Use white rice flour for the lightest, crispest crust.
- Granulated monk fruit sweetener. Sweetens the crust without refined sugar. I use Lakanto Classic Monk Fruit Sweetener, which measures just like sugar.
- Oat flour. I like to use organic oat flour, since conventional oats are often sprayed with glyphosate before harvest. Choose certified gluten-free oat flour if you need the recipe fully gluten-free, since regular oats can be processed alongside wheat.
- Lemon juice and room temperature eggs. Fresh lemon juice tastes brighter than bottled. Room temperature eggs whisk smoothly into the honey and lemon juice, so the custard bakes up even.
Low Oxalate Gluten-Free Lemon Squares
Print Recipe
Ingredients
Crust
- 3/4 cup rice flour
- 1/4 cup cornstarch
- 3 Tbsp granulated monk fruit sweetener
- 1/2 cup salted butter cold, cut into small cubes
Lemon Custard
- 3 large eggs room temperature
- 2 large egg yolks room temperature
- 1/4 cup oat flour
- 2 tsp cornstarch
- 1/3 cup honey
- 1/3 cup lemon juice fresh, about 2 lemons
- 1/4 tsp sea salt
Topping (optional)
- powdered Lakanto monk fruit sweetener optional, for dusting
Instructions
Crust
- Preheat the oven to 325°F. Grease the bottom and sides of an 8×8 inch baking pan with butter.
- In a bowl, combine the rice flour, cornstarch, and monk fruit sweetener.
- Cut in the cold butter with a pastry cutter or fork until the mixture is crumbly and the butter pieces are about pea sized.Food processor option: If you have a food processor, you can use it instead of a pastry cutter or fork. Add the rice flour, cornstarch, and monk fruit sweetener and pulse a few times to combine. Add the cold butter cubes and pulse in short bursts until the mixture starts to thicken and clump together a bit.
- Press the mixture firmly and evenly into the bottom of the pan.
- Bake for 25 to 30 minutes, until the edges are lightly golden.
- Remove from the oven and let the crust cool for 10 minutes. Leave the oven on.
Lemon Custard
- While the crust cools, whisk the eggs and egg yolks together in a bowl. Whisk in the oat flour, cornstarch, honey, lemon juice, and sea salt until smooth.
- Pour the custard over the baked crust.
- Bake for 25 to 30 minutes, until the custard is firm and holds its shape with no jiggle in the center.
- Let the lemon squares cool on the counter for 20 minutes before slicing into 16 squares.
Topping (optional)
- Optional: Just before serving, dust the tops of the squares with powdered Lakanto monk fruit sweetener. Dust right before serving, since the powder slowly soaks into the lemon layer as it sits.
Tips for Low Oxalate Gluten-Free Lemon Squares
- Keep the butter cold. Cut it in straight from the fridge. Cold butter makes a crisp, tender crust.
- Press the crust evenly. Use the bottom of a measuring cup to pack it into a flat, even layer, especially in the corners.
- Pour the custard onto a warm crust. Adding the filling while the crust is still warm helps the two layers hold together.
- Check for set, not color. The custard is done when the center no longer jiggles. Overbaking can make it rubbery.
- Cool before cutting. Let the lemon squares sit on the counter for 20 minutes before slicing. Wipe the knife between cuts.
Storage and Reheating
- Serving. Lemon squares can sit out for up to 2 hours while serving. The filling is made with eggs, so return leftovers to the fridge.
- Refrigerator. Keep in an airtight container for up to 5 days. They taste best served cold.
- Freezing. Freeze the squares in a single layer until firm, then wrap and store for up to 2 months.
- Thawing. Thaw overnight in the refrigerator and serve chilled.
Substitutions and Variations
- Use lime juice instead of lemon juice for tangy lime squares. Limes are low oxalate too.
- Use maple syrup instead of honey in the custard, both are low-oxalate sweeteners.
Frequently Asked Questions
Are these lemon squares low oxalate?
Yes. Rice flour, cornstarch, oat flour, butter, eggs, honey, and lemon juice are all on the low oxalate list. The recipe skips the usual high oxalate ingredients in lemon bars, like wheat flour and almond flour.
Can I use bottled lemon juice?
Yes, it works, but fresh lemon juice gives a brighter flavor. You will need about 2 lemons for 1/3 cup of juice.
How do I know when the lemon squares are done?
The custard should be firm and hold its shape, with no jiggle in the center when you gently shake the pan. This usually takes 25 to 30 minutes at 325°F.
How long should lemon squares cool before cutting?
Let the baked lemon squares sit on the counter for 20 minutes before cutting.
Are these lemon squares gluten-free?
Yes, when made with certified gluten-free oat flour and gluten-free ingredients. The shortbread crust uses rice flour and cornstarch instead of wheat flour, and the lemon filling uses oat flour and cornstarch.