Bake quick, flaky Blueberry Lemon Donuts with puff pastry and fresh blueberries for a bright, buttery treat.
Preheat the oven to 400°F and line a rectangular baking sheet with parchment paper. While the oven warms, make sure the sheet is evenly covered with the paper so the assembled pastries will lift cleanly after baking. This step is straightforward but important — a well-prepared sheet keeps the bottoms dry and encourages even browning.
On a lightly floured work surface, unfold the thawed puff pastry sheet and re-flour the surface lightly to prevent sticking. Using a 2-inch round cutter, press straight down and cut out twelve even circles, keeping the scraps together to re-roll if necessary. Arrange the circles nearby on a floured parchment to keep them from sticking as you work.
Place six pastry circles onto the prepared parchment-lined baking sheet. Top each bottom circle with a small scatter of fresh blueberries, a light pinch of lemon zest and a sprinkle of sugar, then cover with a second circle. Use the tines of a fork to crimp and seal the edges neatly so the filling stays tucked inside; repeat to make six filled donuts in total. Brush the tops gently with beaten egg to give them a glossy finish and cut two small slits in each top to vent steam.

Transfer the prepared sheet back to the oven and bake the sealed donuts for about 10 minutes, watching for a deep golden brown and a slightly glossy, puffed surface. The slits will open slightly, letting a peek of deep-blue filling show through; the exterior should be crisp and layered while the interior remains tender.
Remove the sheet from the oven and let the donuts rest on the parchment for a minute so they settle and the juices don’t run. Gently transfer them to a serving board or platter, arranging them into an inviting stack and scattering a few fresh blueberries and thin lemon slices around to echo the flavors.
Serve the blueberry lemon donuts right away, still warm, with the flaky layers visible and the glossy sugar-sprinkled tops catching the light. They’re best enjoyed fresh from the oven when the filling is still slightly molten and the dough is at its tenderest.
