Grapefruit Layer Cake

granulated sugar ((2 cups))

Zest of 2 large grapefruit

unsalted butter (at room temperature)

eggs (at room temperature)

fresh grapefruit juice

cake flour ((3 cups))

baking powder

salt

buttermilk ((1 cup), at room temperature)

unflavored gelatin powder ((optional, see note below))

cold water

unsalted butter (at room temperature)

granulated sugar ((1 1/2 cups))

eggs

egg yolks

fresh grapefruit juice

fresh lemon juice

Pink and orange food coloring

unsalted butter (at room temperature)

powdered sugar ((6 cups))

fresh grapefruit juice

salt

Pink and orange food coloring

lbs fondant ((I like homemade marshmallow fondant))

Yellow, orange, ivory, and pink food coloring (I like Americolor gel brand)