Making the California Open Faced Tuna Melt is simple when you follow these clear steps:

1. Preheat the Oven: Preheat your oven to 375°F (190°C). This will ensure it’s hot enough to melt the cheese perfectly.
2. Prepare the Tuna Salad: In a large bowl, combine drained tuna, mayonnaise, Dijon mustard, lemon juice, chopped celery, and red onion. Mix well and season with salt and pepper to taste.
3. Toast the Bread: Place slices of sourdough on a baking sheet. Toast them in the preheated oven for about 5-7 minutes or until they are lightly golden.
4. Assemble the Tuna Melt: Remove the toasted bread from the oven. Top each slice with a generous amount of the tuna salad mixture.
5. Add Cheese: Sprinkle the shredded cheddar cheese evenly over the tuna salad on each slice of bread.
6. Bake: Return the baking sheet to the oven and bake for an additional 5-8 minutes, or until the cheese is gooey and bubbly.
7. Garnish and Serve: Remove from the oven. Garnish with fresh herbs if desired, and serve hot.

Following these straightforward steps will lead you to enjoy the wonderful flavors of a California Open Faced Tuna Melt!