Tomato-Mozzarella Gratin

Ingredients

• 5 large tomatoes, sliced
• 1 (8 ounce) ball fresh mozzarella cheese, thinly sliced
• 1/2 teaspoon dried oregano, or to taste
• 1/2 teaspoon garlic powder, or to taste
• 1 pinch herb salt, or to taste
• freshly ground black pepper to taste
• 2 tablespoons dry bread crumbs
• 2 tablespoons grated Parmesan cheese
• 2 tablespoons butter at room temperature, cut into cubes
• 1 tablespoon chopped fresh parsley, or to taste