Step 1

Bake pie crust according to packaging instructions.

Step 2

In a medium mixing bowl, combine the sugar, cornstarch, and salt with a whisk (this will help the cornstarch from lumping). Add the eggs and lemon juice. Mix into a thick paste.

Step 3

Bring the vinegar and water to a simmer in a medium saucepan. Pour a quarter of the hot liquid into the egg/sugar slurry and whisk until smooth.

Step 4

Pour the remaining liquid into the mixing bowl and gently whisk until thoroughly combined. Return the mixture to the saucepan and continue heating, gently whisking continually, until the mixture begins to thicken.

Step 5

Continue for one more minute, then remove from heat.

Step 6

Add the butter and whisk until the butter is melted and combined.

Step 7

Pour into a pre-baked pie shell and allow pie to cool to room temperature.