- 12 tablespoons (1% sticks) unsalted butter, chilled and cubed (6 ounces, 170 grams)
- 1½ cups all purpose flour (6.75 ounces, 195 grams)
- ½ cup confectioners sugar (2 ounces, 57 grams)
- ¼ teaspoon salt (1.25 grams)
- 1½ cups granulated sugar (10.5 ounces, 300 grams)
- 2 tablespoons all-purpose flour (.56 ounce, 16.25 grams)
- ½ teaspoon baking powder (2.45 grams)
- Finely grated zest of 1 lime
- Finely grated zest of 1 blood orange
- Pinch of salt
- 4 large eggs (6.8 ounces, 193 grams), at room temperature
- 1/3 cup freshly squeezed lime juice (2 to 3 limes) (2.9 ounces, 83.3 grams)
- 1 cup freshly squeezed blood orange juice (8 ounces, 225 grams)
- Zester
- Food Processor
- 9-by-13-inch baking pan
- For the Crust:
- Position a rack in the center of the oven and preheat to 350°F. In a food processor, pulse together all the ingredients for the shortbread until the mixture just begins to hold together in large pieces. Turn the dough out into a 9-by-13-inch baking pan and press it into a single layer covering the bottom of the pan. Smooth the top with a rubber spatula. Bake on the center rack, rotating the pan halfway through, until golden and firm to the touch, 20 to 25 minutes. Remove from the oven and reserve.
- For the Filling:
- In a large bowl, whisk together the sugar, flour, baking powder, citrus zests, and salt. In another bowl, whisk together the eggs and citrus juices. Pour the liquid ingredients into the dry ingredients in two additions, whisking until smooth. Spread the filling over the baked shortbread.
- To Bake:
- Bake on the center rack until it is just set, about 15 minutes. Cool in the pan, then cut into squares.