Prepare homemade refried beans by bringing the black beans to a simmer in a pot with a few splashes of veggie broth. Mash until partially smooth, then stir in spices, salt and pepper to taste.

Meanwhile, slice buns/rolls in half lengthwise. Spread a layer of mayo onto each half and place, facing mayo side up, on a baking sheet. Top each with a generous layer of the refried beans. Sprinkle on began cheese if using.

Bake at 350 for about 7 mins or until buns become firm/toasted and cheese begins to melt.