Preheat oven to 350°F (175°C).
Slice slider buns horizontally, keeping them connected if possible, and place in a rectangular baking dish.
Layer the bottom buns with sliced turkey breast and cheddar cheese evenly.
Place the top buns over the cheese and turkey layers.
In a small saucepan, melt the unsalted butter over low heat.
Add minced garlic, Dijon mustard, dried parsley, onion powder, salt, and black pepper to the melted butter. Stir well to combine.
Brush the garlic butter mixture generously over the tops of the slider buns.
Cover the baking dish with aluminum foil and bake for 15 minutes.
Remove the foil and bake for an additional 10 minutes or until the tops are golden brown and cheese is melted.
Serve the sliders warm, arranged on a wooden board.