Directions
<ol class="no-list-style"><li class="MethodStepper"><h4 class="step-title">Step 1</h4>Start by making the pie crust. In a large bowl or food processor, combine the flour, sugar, and salt. Add the cold cubed butter and pulse or use a pastry cutter to work it into the flour until you have pea-sized pieces. The varying sizes of butter create pockets of steam during baking, resulting in flaky layers.</li><li class="MethodStepper"><h4 class="step-title">Step 2</h4>Mix the ice water and apple cider vinegar in a small cup. Drizzle 6 tablespoons of this mixture over the flour mixture and gently combine until the dough just begins to come together. If needed, add the remaining water 1 tablespoon at a time. The dough should hold together when squeezed but shouldn't be sticky.</li><li class="MethodStepper"><h4 class="step-title">Step 3</h4>Divide the dough into two equal portions, form into discs, wrap in plastic wrap, and refrigerate for at least 1 hour or up to overnight. Cold dough is essential for a flaky crust as it prevents the butter from melting before hitting the hot oven.</li><li class="MethodStepper"><h4 class="step-title">Step 4</h4>While the dough chills, prepare the filling. In a large bowl, combine the chopped rhubarb, both sugars, cornstarch, cinnamon, salt, vanilla extract, and lemon zest. Gently toss everything together and let stand for 15 minutes to allow the rhubarb to release some juices and the sugar to begin dissolving.</li><li class="MethodStepper"><h4 class="step-title">Step 5</h4>Preheat your oven to 200°C (400°F) with a rack in the lower third position. Place a baking sheet on the rack to preheat (this helps the bottom crust bake properly).</li><li class="MethodStepper"><h4 class="step-title">Step 6</h4>On a floured surface, roll out one disc of dough to about 30cm (12 inches) in diameter and 3mm (1/8 inch) thickness. Carefully transfer it to your pie dish, gently pressing it into the corners without stretching. Trim the edges, leaving a 2cm overhang. Refrigerate while you roll out the second disc.</li><li class="MethodStepper"><h4 class="step-title">Step 7</h4>For the top crust, roll the second disc to the same dimensions. For a lattice top, cut the dough into 2.5cm (1-inch) strips using a pastry wheel or knife. For a traditional top crust, keep it whole but cut a few vents for steam to escape.</li><li class="MethodStepper"><h4 class="step-title">Step 8</h4>Give the rhubarb filling a final stir and pour it into the chilled bottom crust, mounding slightly in the center. The cornstarch will thicken the juices during baking, preventing a soggy bottom.</li><li class="MethodStepper"><h4 class="step-title">Step 9</h4>For a lattice top, lay half the strips across the pie in one direction. Fold back every other strip halfway, then place a strip perpendicular to them. Unfold the strips over the perpendicular one. Repeat this weaving process until the lattice is complete. For a solid top crust, simply place it over the filling.</li><li class="MethodStepper"><h4 class="step-title">Step 10</h4>Trim excess dough and crimp the edges by pinching between your thumb and forefinger to create a decorative seal. Brush the top with egg wash and sprinkle generously with coarse sugar for a beautiful sparkle and crunch.</li><li class="MethodStepper"><h4 class="step-title">Step 11</h4>Place the pie on the preheated baking sheet and bake for 20 minutes at 200°C (400°F). Then reduce the temperature to 180°C (350°F) and continue baking for 35-40 minutes more, until the crust is deeply golden and the filling is bubbling vigorously through the lattice. If the edges brown too quickly, cover them with foil.</li><li class="MethodStepper"><h4 class="step-title">Step 12</h4>Allow the pie to cool completely on a wire rack for at least 3 hours before slicing. This crucial resting time allows the filling to set properly - cutting too soon will result in a runny pie. For the cleanest slices, refrigerate for 1 hour after cooling completely.</li></ol>