Preheat the oven to 350°F.

In a food processor, combine gingersnap crumbs, melted butter, brown sugar, and salt. Pulse until moistened.

Press the mixture firmly into a deep 9-inch pie dish, pressing into the bottom and sides.

Bake for 12–13 minutes until crisp and lightly darkened. Let cool completely.

In a saucepan, combine cranberries, 1 cup sugar, and ¼ cup water. Bring to a boil, then simmer 15–20 minutes until thick like cranberry sauce.

Carefully puree the cranberry mixture until very smooth.

Add eggs, egg yolks, zest, juice, salt, and remaining ½ cup sugar. Pulse to combine.

Transfer mixture to a heatproof bowl set over simmering water. Stir constantly 15–20 minutes until thickened and reaches 165°F.

Strain the curd through a fine-mesh strainer and let cool until just warm.

Beat the curd, adding butter one piece at a time, until smooth and lighter in color.

Pour filling into cooled crust, smooth the top, and chill at least 8–10 hours or overnight.

Serve with whipped cream and sugared cranberries if desired.