Preheat oven to 350 degrees and grease a 9×13 baking dish.
Heat butter in the microwave until it’s nearly melted (30 seconds or so). Pour into a large bowl and let cool for a minute or two.
Whisk in the brown sugar, eggs, and vanilla. In another bowl, mix the flour, baking soda, and salt and then add the flour mixture to the sugar mixture.
Mix in the butterscotch caramel sauce and then gently fold in the butterscotch chips.
Pour mixture into a baking pan and sprinkle the broken pretzels overtop. Bake for about 45 minutes, checking for doneness around the 35 minute mark. The center should be set and a toothpick should come out clean.