Preheat the oven to 350 degrees F. Line a baking sheet with foil.
In a mixing bowl, combine the softened butter, minced garlic, Parmesan cheese, parsley, and salt until evenly mixed.
Place the loaf on the baking sheet. Use a serrated knife to score the bread in a grid pattern, cutting down almost to the bottom but not through.
Spread the garlic butter mixture into the cuts, working it between the sections as evenly as possible.
Wrap the loaf loosely in foil and bake for 15 minutes. Unwrap and bake 5 more minutes until the top is lightly golden.
Warm the marinara sauce in a small saucepan over low heat. Serve it in a bowl alongside the bread for dipping.