Preheat the oven to 325° F and lightly spray a 9x13-inch baking dish with nonstick cooking spray. In a large bowl, whisk the baking mix, brown sugar, and cinnamon together, breaking up any clumps of brown sugar. Scoop out 1 cup of the combined mix and set it aside in a small bowl.
In another bowl, whisk the eggs, buttermilk, and sour cream together. Pour the wet mixture into the large bowl of dry mix and stir until just combined. Pour the batter into the prepared dish.
Take the reserved dry mix and add the pecans and butter. Use your fingers (or two forks) to blend the butter into the mix and create a crumbly texture. Sprinkle it evenly over the batter.
Bake for 35 to 45 minutes or until a toothpick inserted in the center comes out clean. Serve warm.
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