Preheat your oven to 350°F (175°C). In a mixing bowl, combine gingersnap cookie crumbs, melted unsalted butter, light brown sugar, and a pinch of kosher salt. Stir until moist and crumbly. Press this mixture firmly into the bottom and up the sides of a 9-inch pie dish to form a sturdy crust.

Place the crust in the preheated oven and bake for 12-13 minutes, until it is set and beginning to darken slightly. The edges should be crisp. Remove the crust from the oven and let it cool completely on a wire rack.

In a medium saucepan, add fresh cranberries along with 1 cup of granulated sugar and enough water to cover the berries. Bring to a boil, then reduce heat and simmer for 15-20 minutes until the cranberries burst and thicken.

Transfer the hot cranberry mixture to a blender or food processor and purée until smooth. Set the purée aside to cool slightly.

In a clean food processor, combine the smooth cranberry purée, large eggs, Meyer lemon zest, Meyer lemon juice, remaining sugar, and a pinch of salt. Pulse until thoroughly combined.

Transfer the combined ingredients to a heatproof bowl over simmering water. Stir continuously for 15-20 minutes until the mixture thickens and reaches 165°F.

Pour the mixture through a fine mesh strainer into another bowl. Gradually add room temperature unsalted butter, blending until smooth.

Pour the filling into the cooled gingersnap crust, smoothing the surface with a spatula. Cover lightly with plastic wrap and refrigerate for at least 8 hours.