For the pie crust: Grind the following ingredients in a food processor or blender/stand mixer; combine flour, sugar, and salt and stir. Add cold cubed butter and pulse until you achieve a crumb-like texture. While pulsing, drizzle in just enough cold water to bring the dough together. Place the mixture on a dusted work surface, flatten into a disc, and wrap in plastic wrap. Place in fridge for about 1 hour.
Place and roll out chilled dough on a dusted surface until 1/2-inch-thick. Gently place it in a greased 10-inch pie plate. Trim off excess dough; discard. Cover with plastic wrap; chill until firm, about 2 hours.
For the custard filling: In a bowl, combine sugar, flour, and milk. Stir until sugar dissolves. Transfer to a saucepan and cook over medium heat, stirring until the mixture thickens and starts to bubble. Cook for 1 more minute. Remove from heat.
Place egg yolks in a bowl. Pour in a little of the custard filling and stir until combined.
Add the this egg mixture to the remaining custard. Bring to a gentle boil, stirring constantly. Cook for 2 minutes. Remove from heat. Add vanilla extract, Then stir. Set aside to cool.
Scatter Macapuno over the crust. Pour in the cooled custard.
Bake in a preheated 350°F oven for 20 to 30 minutes or until the crust is cooked through.
Cool on a wire rack. Cover and chill for 10 minutes before serving.
