I set out to forge a single recipe that could stand out at a picnic or potluck, and also sweep confidently into a dinner party in tart form.
Lemon bars belong to the family of bar cookies: Along with brownies, pumpkin bars and dream bars, they are distinctly American sweets. Tarte au citron is one of the defining French desserts, and there are hardly any recipes more British than shortbread and lemon curd. Lemon chess pie, beloved in the South, has a similar flavor profile.
But lemon bars have a thick bottom layer, between a pie crust and a cookie, that makes it possible to pick them up and eat them with fingers instead of a fork — a very American quality. The challenge for me, as for Ms. Lydon, is that everyone already seems to have a favorite recipe.
Lucy’s Lemon Squares have built a substantial fan base since 1969, when the recipe was first published in “The Peanuts Cook Book.” It is a basic and excellent recipe — and tart, like Lucy Van Pelt, the character for whom it’s named. Baking blogs frequently rework the standard lemon bar with buzzy variations like cardamom crusts and Meyer lemon fillings (though Meyer lemons actually make dull lemon bars because they are so low in acidity).
And generations of bakers have been influenced by the changing versions in classic references like Junior League cookbooks and “Joy of Cooking,” which started out very plain but, over the decades, adopted new ingredients like double-acting baking powder and sweetened flaked coconut.