Bright, buttery orange bars with a tender shortbread crust and a tangy-sweet orange custard. Simple ingredients, big citrus flavor—perfect for spring gatherings or any time you crave citrus.
Preheat oven to 350°F. Line an 8x8 inch baking pan with parchment, leaving overhang for easy removal.
Make the crust: In a bowl, stir together 1.0 cup flour, 0.25 cup powdered sugar, and 0.25 tsp salt. Add 0.5 cup melted butter and mix until evenly moistened crumbs form.
Press crust mixture firmly and evenly into the prepared pan. Bake 15 minutes until lightly golden at the edges.
While the crust bakes, whisk the filling: In a medium bowl whisk sugar and eggs until smooth. Whisk in orange zest, orange juice, lemon juice (if using), vanilla, and 0.125 tsp salt. Sprinkle in 0.33 cup flour and whisk just until smooth with no lumps.
Pour filling over the hot crust. Return to oven and bake 18 to 20 minutes, until the center is just set and no longer jiggly.
Cool completely in the pan on a rack, then refrigerate 30 minutes for cleaner slices. Lift out using parchment, dust with powdered sugar if desired, and cut into 16 bars.
Notes
For the best flavor, use fresh oranges and include the zest. Bars keep refrigerated for up to 4 days; freeze (without powdered sugar) tightly wrapped for up to 2 months.