Slice baguette diagonally about 1 inch thick.
Spread butter on both sides. Bake at 350°F or 170°C for 15 minutes total. Flip halfway.
Drain the tuna chucks from a can and store in a bowl. Add mayonnaise, paprika powder, salt, black pepper, and 1 tbsp chopped parsley (optional). Stir to combine.
Spread about 1 tbsp tuna melt on each sliced baguette. Topped with shredded mozzarella. Broil until mozzarella has melted. Garnish with parsley.
Tuna Melt Bruschetta is ready to serve.