Combine cranberries and water in a saucepan. Cook over medium heat until cranberries have burst.Process cranberries in food processor until smooth (don't worry, you can strain out the bits of skin later); or you can puree in a food mill.Create a water bath by placing a saucepan of water over heat to simmer.
Whisk together the sugar and eggs in a metal bowl.
Whisk in the cranberry puree, lemon juice, and salt.
Place the bowl over the saucepan of simmering water, making sure the bottom does not touch the water. Cook the mixture, whisking constantly, until the curd reaches 180 degrees and thickens. Keep whisking while the mixture is heating up to prevent the eggs from cooking.Take the curd off the heat and strain it into the bowl of a food processor or blender.
Let the curd rest for a bit until it cools to about 140 degrees.
Add in the butter pieces a few at the time and combine on high speed. Once all of the butter has been added, let the mixture combine for a few minutes longer to ensure the mixture is perfectly smooth.
Pour curd into a container and let it chill in the refrigerator for about half an hour before assembly.For the crust:Preheat oven to 325 degrees F. Process cookies in food processor until they are finely ground.
Combine cookie crumbs and butter. Press mixture into bottom and sides of a 12-square mini tart pan, or a 9 in round tart pan with removable bottom.
Bake for about 10 minutes until dark brown and firm.
Remove and let cool.To assemble:When you are ready to serve, fill the tart shells with the cranberry curd.
