HEAT oven to 350°F.
BEAT first 5 ingredients in large bowl with mixer 3 min. Stir in carrots and 1 cup nuts.
POUR into 13x9-inch baking dish sprayed with cooking spray.
BAKE 35 to 40 min. or until toothpick inserted in center comes out clean. Cool completely.
BEAT cream cheese and butter in large bowl with mixer until blended. Gradually beat in sugar. Add lemon zest and juice; mix well. Spread onto cake. Sprinkle with remaining nuts just before serving.