Preheat oven to 350 degrees.
Grease a 15x10x1 inch baking pan.
In a large bowl, whisk together the flour, sugar and baking soda.
In a small saucepan over medium high heat whisk together the Dr. Pepper, butter and cocoa.
Bring just to a boil.
Pour the chocolate mixture into the flour mixture and stir until just combined.
Add the eggs, stirring them in quickly.
Transfer to your prepared pan spreading it out evenly.
Bake until a toothpick inserted in the middle comes out clean about 18 minutes.
Remove the cake from the oven and let cool completely.
For the icing in a small saucepan over medium heat whisk together the butter, Dr. Pepper, cocoa, powdered sugar and vanilla until smooth.
Once it starts to bubble shut it off and let cool slightly before pouring over the cake.
Sprinkle with toasted pecans.
Slice and serve!