Preheat and Prepare: Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish or line it with parchment paper.
Mix the Dry Ingredients: In a large bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
Combine the Wet Ingredients: In a separate bowl, beat the sugar, melted butter, and eggs until light and creamy. Stir in the buttermilk and vanilla extract.
Create the Batter: Gradually add the dry ingredients to the wet mixture, folding gently until just combined. Do not overmix.
Pour and Spread: Pour the batter into the prepared baking dish and spread it evenly.
Prepare the Topping: In a small saucepan, combine the sweetened condensed milk, heavy cream, and brown sugar. Cook over low heat until the sugar is dissolved and the mixture is smooth. Remove from heat and stir in nuts or coconut if using.
Add the Topping: Gently drizzle or spoon the gooey topping over the cake batter. Don’t worry if it looks uneven—it will spread beautifully as it bakes.
Bake to Perfection: Bake for 30-35 minutes, or until a toothpick inserted in the center of the cake comes out clean. The topping should be golden and bubbly.
Cool and Serve: Allow the cake to cool slightly before slicing. Serve warm for the ultimate gooey experience, or let it cool completely for a firmer topping.
