01 - Preheat oven to 350°F. Lightly grease a 12-cup mini muffin tin or tartlet pan with cooking spray or a small amount of coconut oil.
02 - Combine flour, sugar, and salt in a medium bowl. Cut in solid coconut oil using a pastry cutter or fork until mixture resembles coarse crumbs. Add cold water 1 tablespoon at a time, mixing until dough just comes together.
03 - Divide dough into 12 equal portions. Press each portion into the bottom and up the sides of each muffin cup to form mini tart shells, ensuring even thickness.
04 - Prick the bottom of each shell with a fork. Bake for 10-12 minutes until edges are lightly golden. Remove from oven and let cool in pan for 5 minutes before transferring to a rack.
05 - Whisk together lemon juice, lemon zest, coconut milk, sugar, cornstarch, turmeric, salt, and vanilla extract in a saucepan until cornstarch is fully dissolved and mixture is smooth.
06 - Place saucepan over medium heat, whisking constantly. Cook for 4-6 minutes until mixture thickens considerably and just begins to bubble. Remove immediately from heat to prevent overcooking.
07 - Pour warm lemon filling evenly into cooled tart shells. Use the back of a spoon or small spatula to smooth the tops level with the crust edges.
08 - Refrigerate tarts for at least 1 hour, or until filling is completely set and firm to the touch. For best results, chill 2-3 hours before serving.
09 - Top tarts with additional lemon zest, fresh berries, or a dusting of powdered sugar just before serving. Serve chilled.