Preheat oven to 350°F. Grease a 9x13-inch baking dish—or line with parchment if you hate dish duty.
In a big ol’ mixing bowl, cream the butter and brown sugar until it looks fluffy and tastes even better.
Beat in the egg like you mean it.
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.
Add the dry mix to the wet mix in batches, alternating with the buttermilk. Don’t overthink it—just don’t overmix.
Fold in the butterscotch chips. Lick the spoon. You earned it.
Spread the batter evenly into your prepared pan.
Bake for 40–45 minutes, or until a toothpick poked in the center comes out clean—or with a few moist crumbs. Not wet. Moist crumbs are cake speak for ‘you’re golden.’
Cool slightly before cutting, if you can wait that long. Otherwise, burn your tongue like the rest of us and enjoy.