Add 1 pound ground beef and ½ finely diced white onion to a large skillet over medium-high heat. Cook for 5–7 minutes, breaking the meat into small pieces, until the onions are translucent and the beef is fully cooked.
Stir in 1 package taco seasoning (or 2 tablespoons homemade taco seasoning) and 1 cup salsa. Bring the mixture to a low boil.
Remove the skillet from the heat.
Preheat the oven to 350 degrees F and spray a 9x13 baking dish with non-stick cooking spray.
Slice 12 Hawaiian rolls or slider rolls in half lengthwise and place the bottom halves into the prepared baking dish.
Spread the beef mixture evenly over the bottom rolls and top with 2 cups shredded Mexican style cheese.
Place the top halves of the rolls over the cheese layer.
In a small bowl, stir together 2 tablespoons melted butter and ½ teaspoon garlic salt.
Brush the butter mixture evenly over the tops of the rolls.
Cover the baking dish with aluminum foil and bake for 15–20 minutes.
Remove the foil and continue baking for 2–5 minutes until the tops of the rolls are golden brown.
Remove from the oven and sprinkle with 2 tablespoons chopped cilantro.
Let cool slightly, then serve warm with optional toppings like salsa, guacamole, lettuce, and tomatoes.
Notes
These sliders are best served fresh, but you can refrigerate the leftovers in an airtight container for up to 3-4 days.