Preheat the oven to 350°F. Grease a 9x13-inch baking pan and lightly flour it, or line it with parchment paper for easier removal.
Mix the Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, and salt until evenly combined.
Cream the Butter and Sugars: In a large mixing bowl, beat the softened butter, granulated sugar, and brown sugar until light and creamy.
Add the Eggs and Vanilla: Beat in the eggs one at a time, mixing well after each addition. Add the vanilla extract and mix until smooth.
Combine the Batter: Add the dry ingredients in batches, alternating with the buttermilk. Mix just until combined. Do not overmix the batter.
Fold in the Pecans: Gently fold the chopped pecans into the batter using a rubber spatula until evenly distributed.
Bake the Cake: Spread the batter evenly in the prepared pan. Bake for 30–35 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
Make the Praline Topping: While the cake is baking, melt the butter in a small saucepan over medium-low heat. Stir in the brown sugar, heavy cream, vanilla, and salt. Cook gently until smooth and bubbling, then stir in the chopped pecans.
Add the Praline Topping: Remove the warm cake from the oven. Immediately pour the warm pecan praline topping evenly over the surface and gently spread it toward the edges.
Cool and Serve: Let the cake cool for at least 15–20 minutes before slicing. Serve slightly warm or at room temperature.