Preheat oven to 325°F (160°C). Line an 8-inch square baking pan with parchment paper and lightly spray the sides with cooking spray.
Beat the butter and sugar until light and fluffy (1–2 minutes). Add eggs, matcha powder, and vanilla extract; mix until well combined.
In a separate bowl, whisk flour and baking powder. Gradually mix in half the dry ingredients, then add the buttermilk, followed by the remaining flour mixture. Do not overmix.
Pour batter into prepared pan and bake for 30–33 minutes, or until a toothpick inserted into the center comes out clean.
Let the cake cool completely. Slice horizontally to create two layers.
Whip butter, powdered sugar, and heavy cream until fluffy. Spread frosting between the layers and on top. Garnish with fresh strawberries.
For extra flair, dust with additional matcha powder or drizzle with white chocolate. Store in an airtight container for up to 3 days in the fridge or freeze for up to 2 months.