1Heat oven to 350°F. In 9-inch square pan or 10-inch ovenproof skillet, heat butter in oven about 2 minutes or until melted. Sprinkle 1/2 cup sugar evenly over melted butter. Spoon berries evenly over sugar mixture.
2In medium bowl, beat remaining ingredients with electric mixer on low speed 30 seconds. Beat on medium speed 2 minutes, scraping bowl frequently. Pour batter over berries.
3Bake about 50 minutes or until toothpick inserted in center comes out clean. Immediately place heatproof serving plate upside down over pan or skillet; turn plate and pan or skillet over. Leave pan over cake about 1 minute so sugar mixture can drizzle over cake; remove pan or skillet. Serve warm. Store cake loosely covered.