Preheat your oven to 350˚F (175˚C) and generously grease a baking sheet with melted butter to prevent sticking.

In a skillet, heat olive oil and unsalted butter over medium heat. Sauté sliced yellow onions for about 5 minutes, then add sugar and cook uncovered until the onions are golden brown, which will take another 5 minutes. Transfer the caramelized onions to a plate.

In the same skillet, combine the au jus mix and water, bringing it to a boil. Reduce the heat and simmer according to package instructions, adjusting water for taste.

Slice the Hawaiian sweet rolls horizontally and spread mayonnaise on the inside. Layer the deli pastrami or roast beef, followed by caramelized onions and provolone cheese on the bottom halves of the rolls.

Cover the assembled sliders with the top half of the rolls. Brush the tops with melted butter and sprinkle sesame seeds on top for added flair.

Place the sliders in the preheated oven and bake uncovered for about 12-15 minutes, until the cheese is melted, and the tops are golden brown.

Cut the sliders into individual portions and serve warm with the aromatic au jus for dipping.