1Heat oven to 350°F (325°F for dark or nonstick pan). Spray bottom only of 8- or 9-inch square pan with baking spray with flour.
2In large bowl, beat cake ingredients with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl occasionally. Pour batter into pan.
3In medium bowl, stir topping ingredients until crumbly, using hands if necessary. Sprinkle evenly over batter in pan.
4Bake 31 to 37 minutes or until toothpick inserted in center of cake comes out clean. Cool at least 30 minutes before serving. Serve warm or cool. Store loosely covered.