Preheat the oven to 350ºF. Grease and flour cake pans. Use 3 6" pans or 2 8" pans.
Line the bottoms with rounds of baking parchment then dust them lightly with flour
With baking spray, put the parchment liner in after you spray the pan
In a large bowl, combine the flour, baking powder, and salt and whisk them gently for even distribution
In a separate bowl combine the milk and vanilla
Using an electric mixer with a paddle attachment, cream the butter and sugar on medium speed until it is light and fluffy, 3 to 4 minutes
Add the eggs gradually, mixing well after each addition, scraping the sides and bottom of the bowl often
Lower the mixing speed to medium-low and add the flour mixture to the butter in 3 parts, alternating with 2 parts of the milk mixture, beginning and ending with the flour
Mix just until it is evenly incorporated, This is a thick, fluffy batter, resembling whipped cream
There should not be any lumps or dry pockets of flour remaining. If the batter has a curdled appearance it has not been mixed enough
Increase the speed to medium and mix for another minute or until it is thick and fluffy.
Divide the batter equally between the prepared cake pans. Weighing the batter into the pans is the most accurate way to do this. This ensures that both layers are uniform in size, and finish baking at the same time
Smooth the batter so it fills the pans evenly,
Bake them for about 30 to 40 minutes, or until the cake is almost ready to pull away from the side of the pan and a toothpick inserted into the center of the cake comes out with a few moist crumbs. Rotate the layers carefully from front to back after 20 minutes, for even baking.
Cool the pans on a rack for 10 minutes, then invert them onto a wire rack that has been sprayed with cooking spray and lift off the pans
Cool them on the rack completely
To assemble the cake:
Place one layer, top side down, on a flat serving plate
Cut several 4-inch-wide strips of parchment or waxed paper to slide under the edge of the layer, to keep the plate clean
Using a thin metal spatula, spread the top of this cake round with a ½-inch thick layer of frosting.
Place the second layer top side up on the first, aligning the layers evenly
Spread a generous layer of frosting around the sides of the cake, rotating the plate as you work so you’re not reaching around the cake to frost the other side
Try not to let any loose crumbs get caught in the frosting
Starting in the center of the cake, cover the top with a generous layer of frosting, taking it all the way to the edge and merging it with the frosting on the sides. Add sprinkles if wanted.
Store the cake at room temperature, preferably under a cake dome, for up to 3 days or refrigerate.