Ingredients
1 cup/230 grams unsalted butter, at room temperature, plus more for pan
1 cup/205 grams granulated sugar
1 teaspoon kosher salt (such as Diamond Crystal)
1 large egg yolk
2 1/2 cups/320 grams all-purpose flour (see Tip)
2 teaspoons ground cardamom
8 tablespoons strawberry jam or any red fruit jam, such raspberry or red currant
1 lemon, for zest
2 tablespoons chopped nuts, such as slivered almonds, chopped walnuts or pistachios
Confectioners’ sugar, for dusting over the top
Directions
1
Butter a 9-inch square metal baking pan and line the bottom and two sides with long strips of parchment, leaving a 1-inch of overhang and creasing the parchment to fit snugly into the pan.
2
Make the dough: In the bowl of a stand mixer fitted with the paddle attachment, combine the butter, sugar and salt. Beat on low speed until incorporated and smooth, scraping down the sides of the bowl as needed, about 3 minutes. (Do not beat until fluffy, you don’t need to incorporate air into the dough.) Add the yolk and mix until just combined. Turn the mixer off and scrape down the sides of the bowl.
3
Add the flour to the bowl all at once and scrape the bottom and sides of the bowl. Turn the mixer speed to low and beat until flour is fully incorporated, scraping the bowl again if needed, about 30 seconds. The dough will be in large crumbles.
4
(If you’re starting with a half batch of Butter Shortbread Dough, start here.) Heat the oven to 350 degrees. Add the ground cardamom and mix with your fingers to incorporate it into the dough. Remove 1 cup of the crumbled dough to a small bowl and refrigerate. Transfer the remaining dough to the buttered pan and flatten into an even layer by pressing into the pan using the flat bottom of a glass. Bake on the middle rack until the edges are golden brown and begin to pull away from the sides of the pan, about 30 minutes. Cool in the pan slightly, for at least 15 minutes.
5
Spread the fruit jam in an even layer over the surface of the crust. Zest the lemon right over the top of the jam, and sprinkle with the chopped nuts and reserved crumble. Return to the oven and bake, rotating once, until the top is golden brown and the jam is sizzling around the edges, about 35 minutes. Cool completely in the pan, at least 1 1/2 hours. Run a knife along the edges to release the sides. Use the parchment to lift the cookie out of the pan onto a cutting board. Dust the top with confectioners' sugar. Cut the cookie into 4 strips, then cut each strip into six 1-inch wide bars.
Notes
If using volume measurements, using a spoon, fluff and scoop the flour into a measuring cup, then scrape with a straight edge to level the surface. This will help prevent adding too much flour which can yield overly crumbly dough.