Preheat oven to 350°F.* Line a baking sheet with parchment paper. Set aside.
Slice the loaf of bread lengthwise into two halves. Place both halves of the bread onto the lined baking sheet, cut side up.
In a small bowl, combine the butter, parmesan, garlic salt, and Italian seasoning. Spread the butter mixture over the cut sides of the bread. Set aside while you make the lasagna mixture.
In a large skillet over medium heat, cook the ground beef, breaking it up with a spatula, until browned and fully cooked, about 5-7 minutes. Drain any excess grease.
Reduce heat to low. Stir in 1 cup of marinara sauce. Simmer for 2-3 minutes, or until the mixture is heated through. Remove from heat and set aside.
Top each half of the loaf with half of the marinara mixture, ½ cup of mozzarella, and ½ cup of cheddar cheese. Bake for 12-14 minutes or until the bread is toasted and the cheese is melted. Broil for an additional 2-3 minutes, watching carefully, until the cheese is golden brown.
Garnish with parsley. Cut and serve immediately with the remaining marinara sauce for dipping.