Preheat oven to 350°F (175°C). Line two baking sheets with parchment paper.
In a medium bowl, whisk together flour, baking powder, baking soda, salt, and freeze dried strawberry powder. Set aside.
In a large bowl, beat softened butter and sugar on medium speed until pale and fluffy, about 2 minutes. Scrape down sides as needed.
Add the egg and vanilla extract, beating on medium speed until smooth, about 1 minute.
With the mixer on low, add the dry ingredients in thirds, alternating with the buttermilk. Mix just until combined, being careful not to overmix.
Gently fold the finely chopped fresh strawberries into the batter with a rubber spatula until evenly distributed.
Using a medium cookie scoop, drop rounded portions of batter onto the prepared baking sheets, leaving 2 inches of space between each mound.
Bake for 10 to 12 minutes until puffed and springy to the touch, or a toothpick comes out clean. Cool on the pan for 5 minutes, then transfer to a wire rack to cool completely.
In a clean bowl, beat softened cream cheese and butter together until smooth and creamy, about 2 minutes.
Gradually add powdered sugar, beating on low to avoid a cloud, then increase speed until light and fluffy.
Transfer filling to a piping bag or zip top bag. Pipe a generous layer onto the flat side of one cooled cake, then gently press a second cake on top. Repeat with remaining cakes.