Preheat oven to 350°.
Melt 1 tablespoon butter in a large nonstick skillet over medium-high heat. Add apple and 2 tablespoons sugar to pan; sauté 7 minutes or until lightly browned. Reduce heat, and cook 5 minutes or until browned, stirring occasionally. Remove from heat.
Melt remaining 1 1/2 tablespoons butter in an 8-inch cast-iron skillet, tipping pan quickly until butter coats sides of pan. Pour melted butter and 1/4 cup sugar into a blender. Lightly spoon flour into a dry measuring cup; level with a knife. Add flour and remaining ingredients to blender; process until smooth. Pour batter into prepared skillet. Top evenly with apple mixture. Bake at 350° for 35 minutes or until a wooden pick inserted in center comes out clean. Cut into wedges. Serve immediately.