In a large mixing bowl, whisk together the all-purpose flour, sugar, baking powder, and salt until well combined. In a separate bowl, beat the eggs, then add the milk and melted butter, mixing until smooth. Gently fold the wet ingredients into the dry ingredients until lump-free.

Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking pan. Pour the cake batter into the prepared pan and spread it evenly. Bake for about 35 minutes or until a toothpick inserted comes out clean. Allow the cake to cool completely on a wire rack.

In a medium bowl, whisk together the evaporated milk, sweetened condensed milk, and heavy cream until smooth. Set it aside.

Once the cooled cake is ready, poke holes all over the surface using a fork. Pour the tres leches mixture evenly over the cake and allow it to soak for at least 1 hour.

In a small bowl, mix together the flour, sugar, and cinnamon for the churro dough. In a saucepan, bring water to a boil and add the butter. Stir in the dry ingredients to form thick dough. Let it cool before frying.

Heat oil in a deep frying pan to 375°F (190°C). Pipe the churro dough into the hot oil, frying until golden brown, about 2-3 minutes per side.

Sprinkle the fried churros with cinnamon sugar and arrange them on top of the soaked tres leches cake. Serve and enjoy!