Preheat oven to 350°.
Beat butter with a mixer at medium speed until creamy; add 3/4 cup brown sugar, beating well. Add egg, beating just until blended.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour and next 4 ingredients; gradually add to butter mixture. (Batter will be stiff.) Add apples, beating just until combined.
Spoon batter into an 8-inch square baking pan coated with cooking spray. Combine 1/4 cup brown sugar and pecans; sprinkle over batter. Bake at 350° for 32 to 35 minutes or until a wooden pick inserted in center comes out clean.