Preheat oven to 350 degrees F. Lightly grease a 9x13" baking pan with cooking spray and set aside.
In a large bowl whisk together the eggs, sugar, milk, vegetable oil and vanilla extract until combined.
Add in 3 cups all-purpose flour, baking powder and salt and whisk until combined. Set aside.
Combine the ingredients for the topping (brown sugar, cinnamon, cold butter and flour) in a medium bowl and use clean hands to pinch the butter into the brown sugar and flour, creating a crumbly and coarse topping.
Pour half of the cake batter into the prepared baking pan and then sprinkle 1/3 of the topping over the batter. Pour the remaining cake batter over the top, then sprinkle the remaining brown sugar topping over the batter.
Bake the cake for 40 to 50 minutes, until a toothpick inserted in the center of the cake comes out clean. Let the cake cool slightly before serving. You may serve the cake warm or let cool completely. Enjoy!