Vinegar pie is a very old fashioned style of pie, one that dates back many, many decades. The idea behind the pie is that shelf-stable vinegar can add a bright tang to a custard pie that would ordinarily use citrus (like lemon) when citrus was out of season. Since we can easily get citrus all year round these days, it gives you an idea of just how far back this style of pie recipe goes! A vinegar pie may not sound appetizing at first thought, but the vinegar is there to contrast with the sugar and prevent the pie from being too sweet, not just to make a pie that actually tastes like vinegar (it doesn’t).
Since I have easy access to citrus, I used a fairly traditional vinegar pie as inspiration for this Key Lime Vinegar Pie. The pie uses no milk and can be made completely dairy free by omitting the butter that is stirred into the filling at the end (the butter serves to make the filling a bit smoother but it is not essential), yet the pie is silky smooth with a texture that is reminiscent of more traditional dairy-based custard and cream pies. The pie has a bright lime flavor thanks to a combination of lime zest and juice, though you’ll only need a couple of key limes to make the pie. Citrus-lovers should enjoy this nontraditional take on a classic key lime.
If you don’t have key limes, you can substitute regular limes. Regular limes are a bit less acidic than key limes are, so I recommend adding in a little extra citrus zest to compensate for that. The pie is delicious on its own, but I prefer to pair it with a scoop of lightly sweetened whipped cream. You can use a regular pastry crust – though it must be pre-baked and cooled before the filling is added – but a graham cracker crust is easier and goes nicely with the creamy filling.
Key Lime Vinegar Pie
4 large eggs
2 cups sugar
5 tbsp cornstarch
1 1/2 oz key lime juice
1/2 oz apple cider vinegar
1 tbsp key lime zest
1/4 tsp salt
2 cups water
1/2 tsp vanilla extract
2 tbsp butter (optional)
9-inch graham cracker crust
Preheat oven to 350F.
In a medium saucepan, whisk together eggs and sugar until smooth. Whisk in cornstarch, lime juice, apple cider vinegar, lime zest and salt until smooth. Whisk in water.
Cook mixture over medium heat, stirring constantly with a whisk or a spatula, until the mixture comes to a simmer and begins to thicken.
Remove from heat and whisk in vanilla extract and butter (if using), stirring until the butter has melted. Pour into pre-baked 9-inch pie shell.
Bake for 15-18 minutes, until filling is set and thickened (bubbles may form on the top of the pie, it’s ok to pop them with a toothpick while the pie is still warm). Allow to cool completely, then refrigerate until thoroughly chilled and firmly set, at least 4-6 hours.
Makes 1 9-inch pie; serves 8.