Step 1

Preheat oven to 350F. Line an 9x13-inch baking pan with aluminum foil for easier cleanup, spray with cooking spray; set aside.

Step 2

To the bowl of a stand mixer fitted with the paddle attachment or large mixing bowl and hand mixer, add the butter and beat on high power to cream it, about 90 seconds.

Step 3

Add the eggs, brown sugar, vanilla, and beat until smooth and well incorporated.

Step 4

Add the flour, baking powder, salt, and mix until just combined, don’t overmix.

Step 5

Add the Rolos and beat momentarily to incorporate.

Step 6

Turn the batter out into prepared pan, smoothing the top lightly with a spatula. It is a very thick batter and can be resistant to spreading easily, but take your time and smooth it out the best you can.

Step 7

Evenly dollop half of the jar of dulce de leche in ping pong ball-sized 'blobs' using a spoon over the surface of the pan. Using the back of a spoon, swirl the dulce de leche over the top. I just did a back-and-forth pattern that wasn't fancy and took about 10 seconds.

Step 8

Bake for about 30 minutes, or until a toothpick inserted in the center should come out clean, or with a few moist crumbs, but no batter. Bars firm up as they cool. Cool for about 2 hours before slicing and serving. Bars will keep airtight at room temp for up to 1 week.