Preheat oven to 350 degrees F. Spray a 9x13 inch baking dish with cooking spray and line with parchment paper.
Make the coconut crust. Pulse the shredded coconut in a food processor until it becomes small crumbs. Add all-purpose flour, butter, sugar, and a pinch of salt, and pulse until combined. Slowly add water while the food processor is running and mix just until combined. Press the crust into the prepared baking sheet in an even layer. Bake for 15-17 minutes or until golden. Remove from the oven and let cool.
Make the pineapple filling. Whisk together sugar with flour, 4 eggs, 1 egg yolk, pineapple juice, lime zest, and lime juice. Pour the filling into the crust and bake for 30-35 minutes or until the edges have set and the center is slightly jiggly. Remove from the oven and cool completely.
Garnish the pineapple coconut bars with toasted coconut and cut them into 15 bars. Sprinkle with powdered sugar if desired.