01 - Set oven temperature to 350°F. Lightly coat a 12-cup mini muffin tin or tartlet pan with oil or cooking spray to prevent sticking.
02 - Combine flour, sugar, and salt in a mixing bowl. Cut in solid coconut oil using a pastry cutter or fork until mixture achieves coarse crumb consistency. Drizzle in cold water one tablespoon at a time, mixing until dough just comes together.
03 - Divide dough into 12 equal portions. Press each portion firmly into the bottom and up the sides of each muffin cup, creating even tart shells with thin, uniform walls.
04 - Pierce the bottom of each shell with a fork to prevent air bubbles. Bake for 10 to 12 minutes until edges turn light golden brown. Remove from oven and allow shells to cool completely in the pan.
05 - Whisk together lemon juice, lemon zest, coconut milk, sugar, cornstarch, turmeric if using, salt, and vanilla extract in a saucepan until cornstarch dissolves completely and no lumps remain.
06 - Place saucepan over medium heat, whisking continuously. Bring mixture to a gentle bubble while stirring, about 4 to 6 minutes, until filling thickens noticeably. Remove from heat immediately once thickened.
07 - Distribute warm lemon filling evenly among the 12 cooled tart shells. Smooth the surface of each tart with the back of a spoon for an even appearance.
08 - Refrigerate tarts for at least 1 hour until filling is completely set and firm. For best results, chill longer to develop firmer texture.
09 - Top with additional fresh lemon zest or whole berries if desired. Serve chilled directly from the refrigerator.