Add lime juice and condensed milk to a large mixing bowl. Stir until evenly combined and lime juice is fully incorporated into the condensed milk. Stir in lime zest.
Pour into pie crust. Level surface with a spatula. Place pie into fridge for several hours or overnight to set. Keep pie in the fridge until ready to serve. If you want to decorate the pie, wait for the filling to set and then decorate. Then put pie back into fridge until ready to serve. You can make the pie 2-3 days in advance.
Notes
You want to leave the pie in the fridge until right before serving because of its creamy filling. When you first take it out of the fridge, the custard will be just firm enough for you to cut through into slices. As the filling comes to room temperature, it will start to soften and won't be as stable for cutting, which is why you want to keep it chilled until right before serving. If you want a more stable filling, try the cream cheese version.
I have only tested this recipe using fresh squeezed lime juice. You can use regular limes or key limes. Regular limes are easier and you will need approximately 6 regular limes to produce the amount of juice needed. If using key limes, you will need approximately 20 key limes.
This recipe uses two 14 oz cans of condensed milk, for a total of 28 oz or 794 grams. 14 oz refers to weight, not volume.
I piped dollops of whipped cream on top and sprinkled on some additional lime zest for decoration.
I used a 9-inch graham cracker pie crust for this recipe. You can also use a 10-inch pie crust but your filling won't be as tall (though it will be a little more stable).
This pie is very sweet but traditional key lime pie is very sweet. If you prefer a less sweet pie, you can make the cream cheese version which will taste more like a lime cheesecake.
Cream Cheese Version: For the cream cheese version, you need 1 (14 oz) can of condensed milk, 1 (8 oz) block of cream cheese, 1/2 cup of lime juice and 1/2 tbsp lime zest. Bring the cream cheese to room temperature first to soften it, then beat it with a mixer until light and fluffy. Then mix in the condensed milk, juice and zest. Pour batter into pie crust. Place the pie into the fridge for several hours until set.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.