1. Heat oven to 350 degrees F. Coat an 8-inch square baking pan with cooking spray; line bottom and two sides with a piece of foil, letting ends extend over sides, and coat foil with spray.
2. Sift together flour and baking powder. In a large bowl, beat egg, egg white, sugar, butter and vanilla until smooth.
3. Beat in flour mixture and oats until blended. Stir in cherries and nuts.
4. Transfer to pan and spread evenly. Bake 20 minutes, or until a tester inserted in center comes out barely clean. Cool completely in pan on a wire rack.