Preheat oven to 350°F (175°C) and grease three 8-inch cake pans.
In a large bowl, cream butter and sugar until fluffy. Add eggs one by one, then mix in vanilla.
In another bowl, whisk together flour, baking powder, and salt.
Alternate adding the dry mixture and milk into the butter mixture until smooth.
Divide batter evenly into three bowls:
Keep one vanilla.
Add cocoa powder to one for the chocolate layer.
Add strawberry puree (and pink coloring if desired) to the third.
Pour into pans and bake for 20–25 minutes or until a toothpick comes out clean.
Let cool fully before frosting.
Stack layers (chocolate, vanilla, strawberry) with frosting between each.
Frost the top and sides, and decorate as desired.