Preheat your oven to 325°F (163°C) and prepare three 8-inch cake pans by greasing them with unsalted butter and lining with parchment paper.

In a medium bowl, whisk together all-purpose flour, baking powder, and salt, then set aside.

In a stand mixer, beat softened butter and granulated sugar on medium speed until light and fluffy, about 4-5 minutes. Add eggs one at a time, mixing well after each. Stir in vanilla extract and dulce de leche.

With the mixer on low, alternate adding the dry mixture and whole milk to the butter mixture, ending with flour. Mix until just combined. Gently fold in honeycomb pieces.

Divide batter evenly between prepared pans and bake for 30-35 minutes or until a toothpick comes out clean. Cool in pans for 10 minutes before transferring to wire racks.

In a saucepan, combine granulated sugar, water, and light corn syrup over medium heat. Bring to a boil until deep golden brown (about 10 minutes). Whisk in cream and salt, then cool.

Beat softened butter with sifted powdered sugar until smooth and creamy. Mix in half of the cooled caramel.

Assemble the cake by placing a layer on a platter, spreading buttercream, and drizzling caramel. Repeat for the second layer. Apply a crumb coat and freeze briefly.

After the crumb coat sets, frost the entire cake with buttercream and drizzle remaining caramel over the top.