01 -
Preheat oven to 350°F (177°C) and line two 12-cup muffin tins with paper liners or lightly coat with nonstick cooking spray.
02 -
In a large mixing bowl, whisk together the butter pecan cake mix, all-purpose flour, and baking powder until evenly combined.
03 -
Add the mashed bananas and large eggs to the dry ingredients. Stir together just until no dry streaks remain; do not overmix.
04 -
Fold 1 cup of chopped walnuts into the batter, reserving the remaining 0.5 cup for topping.
05 -
Divide the batter evenly among the muffin cups, filling each about two-thirds full to allow space for rising.
06 -
Sprinkle the reserved 0.5 cup chopped walnuts over the tops of the filled muffin cups. Bake for 17–20 minutes on the middle oven rack, until muffins are golden brown and a toothpick inserted in the center comes out clean.
07 -
Allow muffins to cool in the pan for 5 minutes, then transfer to a wire rack to finish cooling or serve warm.