We wanted a gluten-free Key lime bar that balanced a tart and creamy topping with a rich, buttery base. Finding a base that would support the topping was easy; we turned once again to the buttery crust we used for our Gluten-Free Ginger-Fig Streusel Bars and our Gluten-Free Lemon Bars. As for the filling, it needed to be sturdy and sliceable. By adding cream cheese and an egg yolk to the usual sweetened condensed milk and lime juice and zest, we created a rich and firm filling that required no precooking before baking. Letting the bars cool for a full 2 hours and then refrigerating them for an additional 2 hours were key to ensuring the custard topping set up. Key limes can be substituted for the regular limes here, although they have a more delicate flavor; you’ll need about 20 to make ½ cup of juice. Do not substitute bottled Key lime juice.
Ingredients
- 6 ounces (1⅓ cups) ATK All-Purpose Gluten-Free Flour Blend
- 2⅓ ounces (⅓ cup) sugar
- ¼ teaspoon salt
- ¼ teaspoon xanthan gum
- 8 tablespoons unsalted butter, cut into ½-inch pieces and softened
- 2 ounces cream cheese, softened
- 1 tablespoon grated lime zest plus ½ cup juice (4 limes)
- Pinch salt
- 1 (14-ounce) can sweetened condensed milk
- 1 large egg yolk
- ¾ cup sweetened shredded coconut, toasted (optional)
- Adjust oven rack to middle position and heat oven to 350 degrees. Make foil sling for 8-inch square baking pan by folding 2 long sheets of aluminum foil so each is 8 inches wide. Lay sheets of foil in pan perpendicular to each other, with extra foil hanging over edges. Push foil into corners and up sides of pan, smoothing foil flush to pan. Spray foil with vegetable oil spray. For the Crust
- Using stand mixer fitted with paddle, mix flour blend, sugar, salt, and xanthan gum on low speed until combined. Add butter, 1 piece at a time, and continue to mix until dough pulls away from sides of bowl, 2 to 3 minutes. (Add 1 to 2 tablespoons water as needed if dough appears dry.) Transfer mixture to prepared pan and press firmly into even layer using bottom of dry measuring cup. Bake until fragrant and beginning to brown, 25 to 30 minutes, rotating pan halfway through baking. Transfer to wire rack and let cool for 30 minutes. For the Filling
- Stir cream cheese, lime zest, and salt in bowl until no lumps remain. Whisk in condensed milk until well combined. Whisk in lime juice and egg yolk until very smooth. Pour filling evenly over crust. Bake until bars are set and edges begin to pull away slightly from sides of pan, 15 to 20 minutes, rotating pan halfway through baking.
- Let bars cool completely in pan, about 2 hours. Cover with foil and refrigerate bars until thoroughly chilled, about 2 hours. Using foil overhang, remove bars from pan. Sprinkle with toasted coconut, if using. Cut into 16 pieces and serve. (Bars can be refrigerated for up to 2 days; crust will soften.)