Preheat oven to 350F (175C). Grease and flour a 9x13 inch baking pan.
In a medium bowl, whisk together flour, baking powder, baking soda, and salt.
In a large bowl, cream together butter and sugar until light and fluffy.
Beat in eggs one at a time, then stir in vanilla.
In a small bowl, combine buttermilk and freeze-dried strawberry powder.
Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk mixture, beginning and ending with the dry ingredients. Mix until just combined. Do not overmix.
Pour batter into the prepared pan and spread evenly.
Bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean.
Let cool in the pan for 10 minutes before inverting onto a wire rack to cool completely.
Frost with desired frosting (cream cheese frosting or strawberry buttercream recommended).
Optional Tips: For a more intense strawberry flavor, add 1/2 teaspoon of strawberry extract to the batter. Buttermilk can be substituted with milk mixed with 1 tablespoon of lemon juice or vinegar. For a gluten-free version, replace all-purpose flour with a gluten-free all-purpose flour blend.