Preheat oven to 350°F (175°C). Grease a 9×13-inch baking pan and line with parchment paper.
Whisk flour, baking powder, and salt in a bowl. Set aside.
In a separate bowl, beat 1/4 cup sugar and egg yolks until pale and thick. Gradually add whole milk while mixing.
Pour batter into the prepared pan and bake for 20-22 minutes until golden and a toothpick inserted in the center comes out clean. Cool 5 minutes.
While cake is cooling, whip egg whites with the remaining 3/4 cup sugar until stiff peaks form. Gently fold into the cake batter and rebake for 8-10 minutes until set. Cool completely in the pan.
In a large bowl, combine sweetened condensed milk, evaporated milk, and vanilla extract, stirring until smooth.
Using a long skewer, poke holes all over the cooled cake. Slowly pour the tres leches mixture over the cake, letting it absorb. Chill for 4 hours or overnight.
Whip chilled heavy cream with powdered sugar until stiff peaks form. Spread a 1/2-inch layer over the cake and arrange sliced strawberries on top.
Refrigerate for at least 30 minutes before slicing.