01 -
Preheat the oven to 350°F. Grease a 9x13-inch baking dish with baking spray or butter.
02 -
In a large bowl, stir the cake mix, mashed sweet potato, sour cream, oil, eggs, and vanilla until smooth and no dry pockets remain.
03 -
In a small bowl, mix the brown sugar, cinnamon, nutmeg, salt, and pecans if using.
04 -
Spread half of the batter into the prepared pan. Sprinkle the cinnamon sugar mixture evenly over the top, then spoon the remaining batter over it.
05 -
Run a butter knife through the batter in wide curves to marble the filling. Bake for 40-45 minutes, until the center springs back and a toothpick comes out with moist crumbs.
06 -
Cool the cake for 10 minutes. Whisk powdered sugar, honey, 2 tablespoons milk, and vanilla until smooth, adding more milk if needed. Drizzle over the warm cake and let set before slicing.