Egg white mixture: in a large bowl, add the egg whites, sugar, and tartar powder, and beat until you see hard peaks when lifting the mixer up.
Egg yolk mixture: in another large bowl, whisk egg yolk, water, vegetable oil until evenly combined. Then add cake flour and baking powder, salt, and whisk to make sure there are no lumps.
Take about ¼ of the egg whites and fold them into the egg yolk mixture, then repeat with the remaining egg whites until the batter is evenly combined.
Transfer batter to the prepared baking pan and smooth the top with an offset spatula.
Bake 350°F(175°C) for 15 mins until light golden brown. Let cool completely.
Make the cream filling: in the bowl of a stand mixer, beat butter and sugar at medium speed until pale and fluffy. Add cream cheese and mix until the mixture is whipped, white and fluffy, about 1-2 minutes until just fully incorporated.
Spread strawberry filling evenly over the cake surface, leaving a 1/2-inch border on the outer short end. Gently roll up the cake tightly. Freeze for 1 hour.
Garnish the cake with dollops of whipped cream and strawberries. Enjoy!