Heat oven to 350°F. Grease 1-quart casserole. In small bowl, beat egg yolks; stir in milk, lemon juice and lemon peel. Add sugar, flour and salt; beat until smooth. In another small bowl, beat egg whites until stiff peaks form. Gently fold yolk mixture into beaten egg whites. DO NOT OVERBLEND. Pour into greased casserole. Place casserole in 13x9-inch pan; pour hot water 1-inchdeep into pan.