Finely grind the macadamia nuts into meal (about 1/16-inch pieces)—this should resemble coarse flour. In a medium bowl, whisk together the remaining flour, cornstarch, and kosher salt. In a separate small bowl, combine the ground macadamia nuts with the 2 tablespoons of flour set aside from the total flour measurement. This separation ensures the nuts distribute evenly throughout the dough without clumping. Zest the lemon fresh and have all ingredients measured and ready before starting the wet ingredients, as this is a dough that benefits from efficient mixing to avoid overworking.

Cut the room-temperature unsalted butter into cubes and place in a large mixing bowl with the sugar. Cream together for 2-3 minutes until the mixture is pale, fluffy, and increased in volume—this incorporates air and creates a tender cookie texture. Add the lemon zest, vanilla extract, and egg yolks, mixing on medium speed until fully combined and the mixture is smooth. The egg yolks act as both a binder and enrichment, creating a rich, tender crumb. I like to make sure the lemon zest is well distributed at this stage so its bright flavor permeates the entire dough.

Add the dry ingredient mixture from Step 1 (flour, cornstarch, and salt) along with the macadamia nut-flour mixture to the creamed butter and sugar mixture from Step 2. Mix on low speed until just combined—stop as soon as no flour streaks remain. Overworking this dough will develop gluten and create tough cookies, so restraint here is key. The dough should come together into a cohesive mass with a slight sandy, nutty texture.

Divide the dough into 2 equal discs, wrap each tightly in plastic wrap, and refrigerate for at least 4 hours (or up to overnight). This chilling time is crucial—it allows the butter to firm up, making the dough easier to roll and cut without cracking, and it also helps develop flavor. While the dough chills, preheat your oven to 325°F about 20 minutes before you're ready to bake, and line your baking sheets with parchment paper.

Remove one dough disc from the refrigerator and roll it out between two pieces of parchment paper to about 1/8-inch thickness (keep the second disc chilled until needed). Cut out circles using a linzer or round cookie cutter—you'll need pairs of cookies, so aim for even circles. For traditional linzer cookies, use a smaller cutter (about 1 to 1.5 inches in diameter) to cut a hole in the center of half the cookies; the uncut cookies will be the bottoms. Transfer all cutouts to a parchment-lined baking sheet and chill for 20 minutes to firm up before baking. Bake at 325°F for about 9 minutes, until the edges are light golden brown but the centers still feel slightly soft to the touch—the cookies will firm as they cool. I prefer slightly underbaked linzer cookies because they stay tender and the jam won't cause them to harden further.

Let the baked cookies cool on the baking sheet for 5 minutes (they'll firm up slightly), then transfer them to a wire rack to cool completely. This prevents the cookies from becoming too soft and breaking apart during assembly. Once cooled, dust the top cookies (the ones with holes) generously with sifted powdered sugar. Spread a thin layer of guava jam onto the flat bottom side of each solid cookie, then carefully place a sugar-dusted cookie on top with the hole-side up, creating a sandwich. For the best texture, I use a thick guava preserve with visible seeds—it adds lovely texture and authentic flavor without being overly sweet.