Preheat oven to 350°F (175°C) and grease your cake pans. Line bottoms with parchment paper.
Sift dry ingredients (flour, sugar, matcha, baking powder, salt) into a bowl.
Add butter and mix until crumbly. Then add egg whites, sour cream, oil, and vanilla. Beat until smooth and fluffy.
Divide the batter evenly into pans. Bake for 35–40 minutes or until a toothpick comes out clean.
Cool cakes completely on a wire rack before layering or frosting.
Make the strawberry buttercream: Heat egg whites and sugar until dissolved, then whip to stiff peaks. Beat in butter, jam, lemon juice, vanilla, salt, and strawberry powder.
Fill and frost the cake using strawberry jam in between layers and buttercream on top.
Decorate as desired use fresh berries, freeze-dried powder, or a matcha dusting!