PREHEAT oven to 325°F. Beat cream cheese, ricotta cheese, 2 of the eggs, 1/4 cup of the sugar, lemon zest and lemon juice in large bowl with electric mixer on medium speed until well blended; set aside.
PLACE flour, butter, remaining 3 eggs, remaining 1/2 cup sugar, milk and baking powder in separate large bowl; beat with wire whisk until well blended. Spread 1/3 of the dough onto bottom of greased 13x9-inch baking dish; cover with cream cheese mixture. Gently spoon remaining dough over top.
BAKE 45 minutes or until center is set. Cut into 16 pieces to serve. Sprinkle with powdered sugar, if desired.