Preheat oven to 350°F (180°C). Lightly spray a 13¾×4½-inch fluted removable-bottom tart pan with cooking spray.

In the work bowl of a food processor, combine flour, cold butter, nuts, confectioners’ sugar, 1 teaspoon (2 grams) lemon zest, and ¼ teaspoon salt; pulse until dough forms large clumps and holds together when pressed between fingers. Press dough into bottom and up sides of prepared pan. Place pan on a rimmed baking sheet.

In a medium bowl, whisk together granulated sugar, eggs, lemon juice, melted butter, remaining 2 tablespoons (9 grams) lemon zest, and remaining ¼ teaspoon salt until smooth and well combined. Pour egg mixture into prepared crust.

Bake until filling is mostly set (it may jiggle just slightly) and crust is golden brown, about 30 minutes. Let cool completely on a wire rack; gently remove from pan, and place on a serving platter.

Spoon Meringue Topping into a piping bag fitted with a small open star tip (Wilton No. 32); pipe as desired. Using a kitchen torch, lightly toast meringue. Serve immediately.