Preheat the oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish.

In a large skillet over medium heat, heat the olive oil. Add the diced onion and cook until softened, about 3 minutes.

Add the ground beef and cook, breaking it up with a spatula, until browned. Drain excess grease if needed.

Stir in the taco seasoning and tomato sauce. Simmer 5–7 minutes, stirring occasionally, until thickened and saucy. Taste and adjust seasoning.

Slice the slider buns in half horizontally. Place the bottom halves in the prepared baking dish and toast in the oven for 5 minutes to help prevent sogginess.

Sprinkle half of the shredded cheese over the toasted bottoms. Spoon the taco meat evenly over the cheese, then top with the remaining cheese.

Place the top halves of the buns on the sliders.

In a small bowl, mix the melted butter with garlic powder, onion powder, and salt. Brush the mixture over the tops of the buns.

Cover the dish with foil and bake for 10 minutes. Remove the foil and bake an additional 5–7 minutes, until the tops are golden and the cheese is melted.

Remove from the oven and let rest 3–5 minutes. Garnish with chopped cilantro. Serve warm with optional toppings such as shredded lettuce, diced tomatoes, red onion, sour cream, salsa, guacamole, and jalapeños.