A sophisticated version of the supermarket standby, these moist cookies keep well.
Cream butter and sugar with the paddle attachment of an electric mixer. Add egg, 1 egg yolk, vanilla, and lemon zest; mix well. Add flour and salt; mix on low speed until dough just comes together. Wrap dough in plastic, and chill until firm, about 1 hour.
Divide dough in half. Roll out one half to fit a 10-by-15-inch baking sheet. Pick up dough by wrapping it around a rolling pin, and unroll it onto baking sheet.
Spread fig filling evenly over pastry. Roll out remaining half of dough, and cover filling. Trim excess pastry to make a perfect rectangle. Chill for 1 hour.
Preheat oven to 375 degrees. Use a paring knife to score dough lightly into 1-by-3-inch bars. Use a fork to prick holes in each bar. Make an egg wash by combining remaining egg yolk with 1 teaspoon water. Lightly brush bars with egg wash. Bake until golden brown, 25 to 30 minutes. Cut into bars, and let cool.