In large bowl, beat 1 1/2 cups brown sugar, the granulated sugar and softened butter with electric mixer on low speed 30 seconds, scraping bowl constantly. Beat on medium speed about 5 minutes, scraping bowl occasionally, until light and fluffy. Beat in eggs, one at a time, beating well after each addition. Add 2 teaspoons vanilla. On low speed, beat in flour mixture alternately with 3/4 cup milk until smooth. Pour into pan.