Set the oven rack in the middle position. Preheat the oven to 400°F. Cover the bottom and sides of a 9 by 13 by 2-inch metal pan with alumi­num foil, shiny side up. Coat the foil with vegetable oil spray. 

To make the filling: Add the water, dates, granulated sugar, salt, lemon zest, and lemon juice to a heavy-bottomed saucepan. Place the saucepan over medium-high heat and bring the date mixture to a boil, stirring constantly with a wooden spoon, until thickened. Cool the filling before spreading it over the oatmeal crust.

To make the bars: Add the flour, salt, and  baking soda to a mixing bowl and whisk to com­ bine. Set aside. Add the rolled oats to another bowl and set aside.

Add the butter, brown sugar, and vanilla to  the bowl of a stand mixer fitted with the paddle attachment and beat until the ingredients are well mixed. Add the dry ingredients and beat to com­ bine. Turn off the mixer, remove the bowl, and fold in the rolled oats. Press half of the flour-oat mix­ ture into the prepared pan. Using an offset spatula, spread with the cooled date filling. Crumble the remaining flour-oat mixture evenly over the filling.

Bake the bars for 30 minutes, or until lightly  browned. Remove from the oven, and transfer to  a wire rack to cool. When completely cool, lift the pastry with the foil from the pan, place on a cut­ ting board, and carefully remove the foil. Cut into  2-inch bars with a wide-bladed knife, wiping the blade with a damp paper towel between cuts. Store the bars between sheets of wax paper in a covered tin at room temperature.

Recipe posted with permission fromBaking with the Brass Sisters: Over 125 Recipes for Classic Cakes, Pies, Cookies, Breads, Desserts, and Savories from America's Favorite Home Bakers