1 package (18.25 ounces) plain yellow cake mix

¼ cup packed light brown sugar

8 tablespoons (1 stick) butter, melted

2 large eggs

1 teaspoon pure vanilla extract

1 cup lightly salted cashews

1 cup butterscotch chips

Place a rack in the center of the oven and preheat the oven to 350 F. Set aside an ungreased 13- by 9-inch baking pan.

Place the cake mix, brown sugar, melted butter, eggs, and vanilla in a large mixing bowl. Blend with an electric mixer on low speed for 1 minute. Stop the machine and scrape down the sides of the bowl with a rubber spatula. Blend again on low speed for 1 minute. Transfer the batter to the pan, smoothing it out with the spatial so that it reaches all sides. Sprinkle the cashew pieces and butterscotch chips over the batter. Place the pan in the oven.

Bake the cake until it is golden brown and a toothpick inserted in the center comes out clean, 27 to 29 minutes. Remove the pan form the oven and place it on wire rack to cool for 30 minutes.

Cut the cake into 24 bars. Remove the bars from the pan with a metal spatula, and serve.

Store the bars, covered in plastic wrap, at room temperature for up to 1 week. Or freeze them, wrapped in aluminum foil, for up to 6months. Thaw the bars overnight on the counter before serving.