Combine flour and cold butter in a food processor until it resembles coarse breadcrumbs.
Add ice water one tablespoon at a time until the dough holds together.
Press dough into mini tart pans and bake at 375°F until golden brown.
Cool shells completely on a wire rack.
Whisk egg yolks, lemon juice, half the sugar, and lemon zest in a bowl set over a double boiler.
Stir continuously until the curd thickens enough to coat the back of a spoon.
Remove curd from heat and let cool.
Beat egg whites with cream of tartar until soft peaks form.
Gradually add remaining sugar while beating until stiff, glossy peaks form.
Fill cooled tart shells with lemon curd and pipe or spoon meringue on top.
Briefly toast the meringue under a broiler until lightly browned.