Line a 13×9-inch baking pan with parchment paper.

In a large bowl, beat butter with a mixer on medium 30 seconds.

Add ½ cup sugar; beat until light and fluffy.

Beat in 1 ½ teaspoons vanilla, the lemon zest and a pinch salt.

Add egg; beat until combined.

Stir in 3 cups flour, mixing until dough comes together.

Pat dough into the bottom and 1 inch up the sides of prepared pan.

Prick dough all over with a fork.

Chill 1 hour.

Preheat oven to 400°.

Cover dough with foil; fill foil with pie weights or dried beans.

Bake 15 minutes.

Remove foil and weights.

Return pan to oven and bake until lightly browned and set, about 10 minutes more.

Remove from oven; let cool on a wire rack.

Reduce oven temperature to 300°.

Spread orange marmalade over baked crust.

For coconut filling, in a metal bowl, combine coconut; the remaining 2 cups sugar, 1 ½ teaspoons vanilla, and ¼ teaspoon salt; and the egg whites.

Set bowl over a saucepan filled with simmering water.

Stir constantly until mixture is hot to the touch (120° to 130°), about 4 minutes.

Remove bowl from heat; stir in the remaining 6 tablespoons flour.

Spread coconut filling over marmalade.

Bake until filling is puffed and golden brown, 45 to 50 minutes.

Cool completely on a wire rack.

For ganache, place chocolate chips in a small bowl.

In a small saucepan, bring cream to a simmer over medium; pour over chocolate chips.

Let stand 5 minutes; whisk until smooth.

Pour ganache over coconut filling and spread evenly.

Let cool to room temperature, then chill until chocolate is set, at least 2 hours.

Cut into small squares.