1. Prepare Oven and Pan:

• Preheat the oven to 350°F (175°C).
• Generously spray a 9×13 inch (or 13×9 inch) baking dish with non-stick cooking spray.

2. Make the Pecan Filling Base:

• In a medium-sized mixing bowl (2-3 quarts), add the 2 cups of packed dark brown sugar, the dark corn syrup, the ½ cup of melted (and slightly cooled) salted butter, the room temperature eggs, and the pure vanilla extract.
• Whisk these ingredients together until they are well combined and smooth.
• Stir in the 3 cups of pecan halves until they are evenly coated with the sweet mixture.
• Pour and spread this pecan mixture evenly into the bottom of the prepared sprayed baking dish.

3. Layer the Cake Mix Topping:

• Sprinkle the dry white cake mix directly from the box as evenly as possible over the pecan filling layer.
• Drizzle the remaining ¾ cup of melted salted butter as evenly as possible over the dry cake mix.
• Sprinkle the remaining ¾ cup of packed dark brown sugar evenly over the melted butter layer.

4. Add Hot Water and Final Pecans:

• Carefully pour the 1 cup of hot water over the top of the dry cake mix, butter, and brown sugar layers. Do not stir or mix this water in. You can gently tilt the cake pan if needed to help distribute the water over the surface.
• Sprinkle the remaining 1 cup of pecan halves evenly over the top of the cake and water layer.

5. Bake:

• Place the baking dish in the preheated oven.
• Bake for 35-40 minutes. Keep an eye on it, as ovens vary – the recipe notes to start checking at the 30-minute mark.
• The cake is done when the topping is golden brown and the edges are bubbly. The center will still be a bit jiggly when gently nudged but should not look liquidy; it will firm up considerably as it cools.

6. Cool Completely:

• Carefully remove the Pecan Dump Cake from the oven and place the pan on a wire rack.
• Allow the cake to cool completely in the pan before serving. This is very important for the gooey filling to set properly and can take several hours.

7. Serve:

• Once completely cool, slice the cake into squares directly from the pan.
• Serve as is, or with an optional drizzle of caramel topping or a scoop of vanilla ice cream. Enjoy this rich and nutty treat!