Filled Oatmeal-Date Cookies

To make filling: Combine dates, brown sugar, lemon juice, lemon zest and water in a small saucepan. Bring to a simmer over medium heat. Cook, stirring, until thickened, about 30 seconds. Set aside to cool. To make dough: Place rack in upper third of oven; preheat to 350°F. Coat 3 baking sheets with cooking spray; set aside. Combine brown sugar, egg, egg whites, oil, apple butter and vanilla in a large mixing bowl. Beat with an electric mixer until smooth and pale in color, about 2 minutes. Sift flour, baking soda, cinnamon, salt and baking powder into the mixing bowl. Add rolled oats and stir with a wooden spoon until well combined. Drop the dough by heaping teaspoonfuls onto the prepared baking sheets, spacing cookies about 1 1/2 inches apart. With the back of a teaspoon, dipped in water to prevent sticking, make a depression in the center of each mound. Fill with a scant teaspoon of the reserved date filling. Top with another heaping teaspoon of dough, spreading it to roughly cover the filling. Sprinkle each cookie with a scant 1/4 teaspoon pecans (or walnuts). Bake, 1 sheet at a time, until lightly browned on top, 12 to 15 minutes. Transfer the cookies to racks to cool.