Preheat your oven to 350°F (175°C) and prepare your baking gear. Grease two 9-inch round cake pans with butter or cooking spray, and line the bottoms with parchment paper.

In a large mixing bowl, combine ½ cup of unsalted butter, 1 cup of granulated sugar, and 1 cup of brown sugar. Beat until light and fluffy, about 2-3 minutes.

Gradually add 3 large eggs to the creamed mixture, one at a time, ensuring each is fully incorporated before adding the next. Mix in 2 teaspoons of pure vanilla extract.

In a separate bowl, whisk together 2 cups of all-purpose flour, 1 tablespoon of baking powder, and ½ teaspoon of salt.

Slowly add the dry flour mixture to the butter mixture while alternating with 1 cup of buttermilk, starting and ending with the dry ingredients.

Gently fold in 1 cup of butterscotch chips into the batter using a spatula.

Divide the batter between the two prepared cake pans, smoothing the tops with a spatula. Bake for 25-30 minutes.

Prepare the crunchy topping by mixing together ½ cup of brown sugar, ¼ cup of melted unsalted butter, 1 cup of oats, and optional ½ cup of chopped nuts.

Once the cakes are done and cooled for about 10 minutes, carefully remove from the pans. Sprinkle the crunch topping over both cakes and bake for an additional 10-15 minutes.

Remove the cakes and let them cool completely on wire racks.