Preheat oven to 325°F. Mix 1 cup each of the flour and sugar, cinnamon, baking soda, nutmeg and salt in large bowl. Add oil, 2 of the eggs, vanilla extract and carrots; mix well. Spread 1/2 of the batter into greased and floured 13x9-inch baking pan. Reserve remaining batter. Set aside.
Beat cream cheese and remaining 1 cup sugar in another large bowl with electric mixer on medium speed until well blended. Add milk, remaining 2 tablespoons flour and lemon extract; beat until well blended. Add remaining 2 eggs, 1 at a time, beating on low speed after each addition just until blended.
Drop spoonfuls of the cream cheese mixture and reserved carrot cake batter, alternately, over the carrot cake batter in pan. Cut through several times with knife for marble effect.
Bake 40 minutes or until toothpick inserted in center comes out clean. Cool in pan on wire rack.