Preheat oven to 350 degrees. Spray a 17x12x1 inch baking sheet with cooking spray.
In medium bowl, whisk together the flour, baking powder and salt. This is the flour mixture.
In small bowl, mix together the buttermilk, honey and vanilla. This is the honey mixture.
In stand mixer bowl, beat the butter and sugar for about 4 minutes until light and fluffy.
Add eggs, one at a time, beating well after each addition and scraping down sides of bowl as needed.
Alternatively add the flour mixture and the honey mixture. Flour, honey, flour, honey and flour. Scrapes the side and give a final mix with your spatula.
Bake for 19-20 minutes, until toothpick inserted into center comes out clean.
Let cool in pans for 10 to 15 minutes on top of a wire rack, then invert to another wire rack.
Vanilla Buttercream
Beat butter on a medium speed for 30 seconds until smooth.
Mix in vanilla extract and salt on a low speed.
Slowly add in 7 cups of powdered sugar, 1 cup at a time. Half way through add in 3 Tbsp of heavy cream or milk to make it easier to mix.
Mix on low until the ingredients are fully incorporated and the desired consistency is reached.
If the frosting is too thick, add in 1 tbsp of cream (1 Tbsp at a time). If the frosting is too thin, add 1/4 cup of powdered sugar. Add the desired color.