Pull-Apart Patty Melt Sliders

1/4 cup mayonnaise
2 Tbsp. ketchup
1 Tbsp. pickle relish
3/4 tsp. granulated garlic, divided
3/4 tsp. onion powder, divided
1/2 cup salted butter, divided
2 tsp. caraway seeds
1 (16 oz.) package dinner rolls (12 rolls)
3 Tbsp. olive oil, divided
3 onions, 2 1/2 sliced and 1/2 finely chopped
1 1/2 tsp. kosher salt, divided
1 1/4 lb. ground beef
2 Tbsp. Worcestershire sauce
1/4 tsp. black pepper
2 cups grated Swiss cheese (about 8 oz.)

Preheat the oven to 400°F. Line a rimmed baking sheet with foil. In a small bowl, mix together the mayonnaise, ketchup, relish, and 1⁄4 teaspoon each of the granulated garlic and onion powder. Set aside.

In a large skillet, melt 6 tablespoons of butter over low heat. Add the caraway seeds and cook, stirring, until lightly toasted and fragrant, about 1 minute. Scrape the seeds and butter into another small bowl. (No need to wipe out the skillet.)

Using a serrated knife, cut the whole pack of rolls in half horizontally, keeping the rolls attached. Place the top and bottom halves cut-side up on the baking sheet. Brush the cut sides with about 4 tablespoons of the caraway butter, including some of the seeds. Toast in the oven until crisp and light golden, about 5 minutes. Set aside; leave the oven on.

Meanwhile, heat the remaining 2 tablespoons of butter and 1 tablespoon of olive oil in the skillet over medium-low heat. Add the sliced onion and 1⁄2 teaspoon salt. Cook, stirring occasionally, until caramelized and golden brown, about 15 minutes. If the pan becomes too dry, add 1⁄2 cup water and stir to deglaze, then continue cooking. Keep warm.

In another large skillet over medium heat, heat the remaining 2 tablespoons of olive oil. Add the beef and season with the remaining 1 teaspoon of salt. Cook, breaking up the meat with a wooden spoon, until no longer pink, 4 to 5 minutes. Add the Worcestershire sauce, pepper, chopped onion, and the remaining 1⁄2 teaspoon each of the granulated garlic and onion powder; cook until the onion is softened and the beef is cooked through, about 4 minutes more.

Spoon the beef mixture over the bottom half of the rolls, spreading it to the edges. Press the meat down lightly to keep it in place. Top with the caramelized onions, then sprinkle with the Swiss cheese. Spread the cut side of the roll tops with the mayonnaise mixture, then flip it over onto the sliders. Brush the roll tops with the remaining caraway butter and seeds. Bake until the cheese is melted and the rolls are crisp and lightly browned on top, about 10 minutes.