Make Lemon Curd: Cut butter into pieces and in a heavy saucepan cook with zest, lemon juice, and sugar over moderate heat, stirring, until sugar is dissolved and mixture just comes to a simmer. In a bowl whisk together eggs and whisk in lemon mixture until combined well. Transfer lemon curd to pan and heat over moderate heat, whisking constantly, until it just begins to simmer. Pour lemon curd through a fine sieve into a bowl and cool slightly.Chill lemon curd, its surface covered with polastic wrap, at least 2 hours, or until cold, and up to 3 days.

Fill tartlet shells in baking cups with lemon curd.Chill tartlets, covered 1 hour. Preheat oven to 400 F.

Make Meringue: In a bowl with an electric mixer beat whites with a pinch salt until foamy. Add cream of tartar and beat whites until they hold soft peaks. Gradually add sugar, beating until meringue holds stiff peaks.

Transfer meringue to a pastry bag fitted with 1/2-inch plailn tip and pipe meringue 2 inches high onto each tartlet, completely covering lemon curd.

Bake tartlets in middle of oven 3 minutes, or until meringue tips are just browned, and cool in cups on racks. Chill tartlets in airtight containers at least 2 hours, or until cold, and up to 1 day. Keep tartlets chilled until ready to serve. Makes 24 tartlets.

Sweet Tartlet Shells: For this recipe you will need two mini-muffin pans, each containing twelve 1 3/4- by 1-inch cups.

Cut butter into bits. In a bowl with a pastry blender or in a food processor blend or pulse flour, confectioners' sugar, and salt until combined well and add butter, blending or pulsing until mixture resembles coarse meal. In a small bowl whisk together yolks, ice water, and vanilla until combined well and add to flour mixture, tossing with a fork or pulsing until incorporated. Form dough into a ball and divide into 2 pieces. Form each piece into a ball and flatten to form disks. Chill disks, wrapped separtely in plastic wrap, at least 1 hour and up to 1 week.

Preheat oven to 400 F.

Form 1 dough disk into twenty-four 1-inch balls, keeping remaining disk wrapped and chilled. Press dough balls into bottoms and up sides of twenty-four 1/8-cup mini-muffin cups (about 1 3/4 inches across top and 1 inch deep). Trim any overhang with a knife and prick bottoms of shells with a wooden pick. Chill shells 15 minutes, or until firm. Bake shells in middle of oven 12 minutes, or until golden, and cool in cups on racks. Gently loosen shells with a knife and remove from cups, reserving shells for chocolate raspberry bites (recipe below).

Make more shells (for lemon meringue bites; recipe above) in same manner but after loosening shells do not remove them from cupss. Tartlet shells may be made 2 days ahead and kept in an airtight container at room temperature. Makes 48 tartlet shells.