Heat the oven to 350 degrees. In a medium bowl stir together the butter, brown sugar, 2 teaspoons lemon zest, flour, oats, walnuts, and baking powder; mix well. Firmly pack the crust mixture into bottom of greased 9-inch baking pan.
In a medium size mixing bowl add the sweetened condensed milk, cottage cheese, egg, lemon juice, and 2 teaspoons lemon zest.
Beat at medium speed for 1 minute. Increase the speed to high; continue beating for 1 more minute. Add the chocolate chips and stir. Pour the filling over the crust.
Sprinkle the filling with cherries and swirl with a knife to mix. Bake the bars for 30 to 35 minutes or until filling is very lightly brown.
Remove the pan from the oven. Cool completely at room temperature before refrigerating for 3 hours.
Before serving the bars, sprinkle top with powdered sugar, if desired and cut into squares. Refrigerate leftovers.