Mix graham cracker crumbs, sugar, salt and melted butter until evenly moist, resembling wet sand.
Transfer mixture into a 9-inch pie dish and press firmly and evenly onto the bottom and slightly up the sides. Set aside.
For the calamansi filling, combine condensed milk, sour cream and calamansi juice or calamansi extract. Stir until smooth and incorporated.
Transfer into prepared pie dish and smoothen the top.
Bake for 10-12 minutes or until tiny bubbles appear on the surface of the pie (usually beginning at the sides). The middle of your pie should have a slight jiggle but set everywhere else.
Remove from oven, allow to cool slightly then chill in the fridge for 4 hours, preferably overnight.
Video
Notes
The number of servings depend on how big your pie slices are. Estimated nutrition information provided is based on 12 servings.
This pie bakes fairly quickly and is easy to over bake. Every oven is different so watch for those tiny bubbles forming on the sides.
I use prepared graham cracker crumbs which are very finely crushed.
I also use bottled calamansi extract because it’s difficult to find fresh calamansi juice where I am. Different brands don't always taste the same so I start with 1 bottle (150-ml) and add to taste. I usually add ¾ cup (190-ml) and I recommend not to go over this amount.