Pulse flour, butter, lard and salt in a food processor until crumbly. Whisk 1 egg with 2 tsp (10 mL) lemon juice; add enough ice water to make 2/3 cup (150 mL). Add to the flour mixture and pulse until the dough comes together. Form into an oblong disk; chill for at least 30 minutes.
Preheat oven to 375°F (190°C). On a well–floured surface, roll dough into a large rectangle, about 1/8–inch (3 mm) thick. Trim dough into a 13 x 18–inch (32.5 cm x 45 cm) rectangle. Carefully transfer dough to a parchment–lined baking sheet.
Stir sugar with cornstarch and lemon zest until combined. Sprinkle half of the mixture evenly down the length of one side of the rectangle, leaving a 1–inch (2.5 cm) border. Arrange cherries evenly over sugar mixture. Whisk 1 tbsp (15 mL) lemon juice with vanilla; drizzle evenly over the cherries. Sprinkle remaining sugar mixture evenly over top.
Fold dough over to cover the filling. Fold an additional 1/2–inch (1 cm) of dough from bottom layer over top layer along the edges; crimp with a fork to seal. Whisk remaining egg with a little water; brush all over pastry. Slash 4 vent holes in top. Bake for 50 to 55 minutes or until golden. Cool completely on baking sheet.
Optional Glaze: Blend icing sugar with milk until smooth. Drizzle evenly over the cooled pie. Makes 12 servings.
Tip: Fold dough into thirds or roll around a rolling pin to transfer it, after trimming, to the baking sheet.