Preheat the oven to 350°F (175°C). Line three 8-inch round cake pans with parchment paper and lightly grease them.
In a large mixing bowl, beat the butter and sugar together until light and fluffy, about 5 minutes.
Add the eggs one at a time, beating well after each addition.
In another bowl, whisk together the flour, baking powder, and salt.
Add half of the dry ingredients to the butter mixture and mix until just combined.
Pour in 1 cup of buttermilk and the vanilla extract, then mix gently.
Add the remaining flour mixture and stir until no dry streaks remain.
Divide the batter evenly among three bowls.
Stir the ground freeze-dried strawberries, remaining tablespoon of buttermilk, and optional pink food coloring into one portion of batter.
Pour each batter into its prepared cake pan.
Bake for 35–40 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
Cool in the pans for 5 minutes before transferring to wire racks to cool completely.