A classic lemon tart requires making a stovetop curd, and too often its flavor winds up harsh and puckery. We found an easier, better way—no stovetop stirring required. We temper the brassiness of lemon with sweeter, gentler orange and simply combine sugar, zest, juice and eggs in a bowl. A little heavy cream softens the sharpness of the citrus. We pour the mixture into a warm prebaked tart shell, then bake it for about 30 minutes. Added to a warm pastry shell, the filling sets more quickly, which helps prevent the crust from becoming soft and soggy. The flavors are boldest if the tart is served at room temperature, but the dessert is more refreshing when lightly chilled. Either way, lightly sweetened whipped cream is a perfect accompaniment.