For the crust
For the lemon pie filling
For the meringue
Preheat the oven to 400 degrees, F. To make the crust, mix the flour, sugar and salt together in a bowl. Add the oil and water and stir the mixture together using a fork, until it starts to form a ball. Pull the mixture together into a ball. Cut the ball in half. Then cut each half into thirds and then each third in half again. You'll have 12 pieces, approximately all the same size.
Press one piece into the cup of a 12 cup muffin tin. Press the crust flat against the bottom of each cup and up the sides. Bake the crusts on the center rack of your oven for 10-12 minutes, until lightly browned. Reduce the oven temperature to 350 degrees F.
While the crusts are baking make the filling. Whisk together filling ingredients in a pan. Cook over medium heat, stirring constantly, until the mixture comes to a boil. Boil for one minute while continuing stirring.
Make the meringue. Beat the eggs whites in a medium bowl until frothy. Add the cream of tartar and continue beating until the egg whites thicken. Add the sugar slowly and continue beating until the egg whites are shiny and form stiff peaks.
Spoon the hot filling into the crusts. Spoon the meringue over the filling making sure to seal the meringue to the edges of the crusts. Return the tarts to the oven to bake for 10 minutes, until the meringue is lightly golden.
Cool the tarts in the tin. They will be easy to remove from the tin once they have cooled.