- 2 (3 ounce) cans white tuna in water, drained
- 2 (1 ounce) slices Swiss cheese, diced
- 2 tablespoons mayonnaise
- 1 1/2 teaspoons sweet pickle relish
- 1/4 teaspoon dried minced onion
- 1/4 teaspoon onion powder
- salt and ground black pepper to taste
- 1 (8 ounce) package fresh white mushrooms, cleaned and stems removed
- Preheat an oven to 350 degrees F (175 degrees C).
- Combine the tuna, Swiss cheese, mayonnaise, sweet relish, dried onion, onion powder, salt, and pepper in a large bowl. Fill mushroom caps with the tuna mixture; place on baking sheet.
- Bake in preheated oven until the mushrooms are soft and begin to give up their juices, 20 to 25 minutes.