1. Heat oven to 325 degrees F. Coat a 13 x 9 x 2-inch baking pan with nonstick cooking spray. In medium bowl, whisk flour, baking powder and salt.
2. With mixer on medium speed, beat butter and agave syrup in bowl until light and fluffy. Add eggs, one at a time, beating after each. Beat in vanilla.
3. On low, beat flour mixture alternately with milk into butter mixture, beating after each addition. Pour into prepared pan.
4. Bake at 325 degrees F for 45 minutes, or until toothpick inserted in center comes out clean. Cool cake completely.
5. While cake cools, prepare Frosting. Beat cream cheese and butter in a large bowl until smooth. Beat in agave syrup until good spreading consistency. Spread onto cooled cake. Store in refrigerator.