The best gluten-free lemon bars has a classic lemon squares taste made with an easy sweet and tangy recipe. A no fail, buttery shortbread crust may be made with gluten free flour or use the included almond flour crust adaptation.
Preheat the oven to 350ºF. Line an 8X8" pan with a large piece of foil, pressed firmly to the bottom and the sides with enough overhang to lift the bars out after baking. Set aside.
For the crust, use a food processor or stand mixer fitted with paddle attachment. On low speed combine the flour, sugar, and salt.
Add the softened butter to the dry ingredients, one tablespoon at a time, blending completely between each addition. The dough should pull away from the sides of the bowl and come together without any dry crumbs.
Pour in the prepared baking pan, pressing firmly into an even layer. Bake for 20-25 minutes, rotating halfway through, until lightly golden brown. Remove from oven, leaving oven on, while the filling is prepared.
For the filling, use a medium saucepan to whisk together the sugar, flour, cream of tartar, and salt. Add the eggs, egg yolks, lemon zest, and lemon juice. Whisk to combine.
Cook over medium-low heat, stirring constantly, until the mixture until the mixture thickens and reaches a temperature of 160ºF, about 5-7 minutes. (I use my favorite instant read thermometer to check quickly.)
Remove from the heat and stir in the butter. Pour the hot filling over the baked crust.
Return to the oven for 10-12 minutes, or until the edges are raised and the filling barely jiggles when the pan is gently shook. Cool the bars to room temperature, then chill for 2 hours in the pan. Lift the bars out of the pan by the foil handles and cut into bars. Dust the tops with powdered sugar and serve. Refrigerate leftovers in an airtight container.
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FREQUENTLY ASKED QUESTIONS
Can I use limes?Yes. If you would like to make gluten free lime bars, replace the fresh lemon juice and zest with equal amounts of lime.
Can I make this recipe dairy free?Yes. Replace the butter with a dairy-free butter (such as Earth Balance butter sticks). However, plant-based butter is a little saltier so I recommend omitting the salt in the recipe.
How can I tell when they are done baking?This recipe has a shortened baking time because the creamy lemon custard filling comes together on the stove top first. While this is an extra step, it does take out some of the guesswork of when the lemon square are done.
The bars should have a raised edges and the middle should be set. It will still jiggle a little when the pan is shook, but shouldn't slosh around.
For best results, cool the bars completely on a wire rack and then at least 2 hours before cutting and serving.
How do I store lemon bars?Store cut lemon bars in the refrigerator in an airtight container. Upon sitting, the powdered sugar will seep into the filling, so you may want to dust them again upon serving.