Preheat the Oven: Preheat your oven to 350°F (175°C). Lightly butter or grease a 9×13-inch baking pan to ensure easy removal after baking.
Prepare the Cake Base: In a large mixing bowl, combine the flour, salt, sugar, and baking powder. Add the milk, eggs, and vanilla extract, then mix until the batter is smooth and well combined. Finally, pour in the melted butter and stir until fully incorporated. The batter will be thick and creamy.
Spread in the Pan: Pour the batter into your prepared baking dish, smoothing the top with a spatula to create an even layer.
Make the Cinnamon Topping: In a separate bowl, mix together the brown sugar, flour, cinnamon, and softened butter until it forms a smooth, spreadable mixture. The consistency should resemble a thick paste.
Add the Topping: Drop spoonfuls of the cinnamon mixture evenly across the top of the cake batter. Use a butter knife to gently swirl the topping through the base, creating marbled ribbons of cinnamon throughout the cake. Avoid overmixing — you want distinct swirls for that signature cinnamon roll look.
Bake: Place the pan in the oven and bake for 28–30 minutes, or until a toothpick inserted in the center comes out clean and the edges are golden brown. The cake should spring back lightly when touched.
