Make the crust:

In a small bowl, combine the cream cheese, butter, and lemon zest until blended.  Gradually cut in the flour and powdered sugar with a pastry blender or 2 forks until a dough forms.

Cover the bowl and chill for 1 hour, or until firm.

Make the lemon curd:

In a medium saucepan, whisk together the eggs, sugar, lemon juice, and zest until smooth

Place the saucepan over medium-low heat.  Stir constantly with a whisk until the mixture comes to a full boil, thickens, and coats the back of a spoon – about 15 minutes.  It should be thicker than heavy whipping cream.

Make a slurry with the cornstarch and 1 teaspoon of lemon juice.  Whisk into the curd and cook, whisking for another minute.

Add the butter, one cube at a time, whisking it in completely before adding another cube.

Whisk vigorously until smooth, thickened, and glossy – about 1 minute.

Pour the hot curd into a glass bowl. Cover with plastic wrap and chill until cold.

Make the filling:

In a small bowl with a hand mixer, beat the sugar and cream cheese together until smooth.

Add the lemon juice and vanilla and mix well.

Add the egg.  Beat the egg into the mixture until well incorporated.

Set aside.

Assemble the tarts:

Preheat the oven to 325 degrees.  Form the dough into 1-inch balls and press onto the bottom and up the sides of 18-24 ungreased mini tart pans.

Fill each tart pan half full with the cream cheese mixture.

Bake for 18-22 minutes or until the middle of each tart is set.

Cool in the tart pans over a wire rack.

When cool, remove the tarts from the pans.

Spoon the lemon curd on the top of each tart.

Store in the refrigerator in a single layer in an airtight container.

Serve cold.