Great-grandma Martha baked this 4 ingredient miracle whenever times were tough and somehow it tastes exactly like sunshine.

Set your unbaked 9-inch pie crust into a ceramic pie plate if it isn’t already in one. Crimp or press the edges as desired, then place the pie plate on a baking sheet to catch any drips and make it easier to move.

In a medium mixing bowl, whisk the eggs until the yolks and whites are fully combined and slightly frothy. This helps the custard bake up evenly.

Add the granulated sugar to the eggs and whisk until the mixture looks thick and glossy and the sugar is well incorporated, about 1 minute by hand.

Pour in the apple cider vinegar and whisk again until the filling is completely smooth. The mixture will be fairly thin—that’s exactly what you want for a silky custard.

Carefully pour the filling into the prepared pie crust. If you like, lightly tap the pie plate on the counter to pop any large air bubbles.

Transfer the pie (on its baking sheet) to the oven. Bake at 375°F (190°C) for 35 to 45 minutes, until the top is golden with slightly crisp edges and the center looks set around the outside but still has a gentle wobble in the very middle when you nudge the pan.

If the crust edges or top begin to brown too quickly before the center is mostly set, loosely tent the pie with a piece of foil and continue baking until done.

Remove the pie from the oven and place it on a cooling rack. Let it cool completely at room temperature; the custard will finish setting as it cools, giving you that smooth, sliceable center.

Once cooled, serve at room temperature or chill for at least 1 to 2 hours for cleaner slices. Store any leftovers covered in the refrigerator and enjoy within 3 days.