Preheat the oven to 350°F (175°C) and grease a 9×13 inch pan. Separate the egg whites and yolks. In a large bowl, beat the egg whites on medium speed until soft peaks form. Gradually add the sugar, ¼ cup at a time, while continuing to beat. Continue until stiff peaks form.
In a separate medium bowl, beat the egg yolks using clean beaters until thick, foamy, and pale yellow. This may take several minutes. Gently fold the whipped yolks into the egg whites until fully combined.
In a small bowl, mix together the flour and baking powder. Gently fold this mixture into the batter just until combined. Do not overmix.
Pour the batter into the prepared pan and bake for about 20 minutes, or until a toothpick inserted in the center comes out clean. Allow the cake to cool completely at room temperature.
In a bowl, whisk together the evaporated milk, sweetened condensed milk, and whole milk until smooth.
Once cooled, loosen the edges of the cake with a knife or spatula. Poke holes all over the surface using a fork or toothpick. Pour the milk mixture evenly over the cake. Cover and refrigerate for at least 3 hours, or overnight.
In a medium bowl, beat the heavy cream, powdered sugar, and vanilla extract until medium peaks form. Avoid overmixing. Spread or pipe the whipped cream over the chilled cake. Garnish with cinnamon and sliced strawberries if desired.