1. Prepare the Tuna: Start by thoroughly draining the two cans of tuna. You can press the lid against the tuna in the can to squeeze out as much water as possible, or transfer it to a fine-mesh sieve and press gently. This step is crucial for preventing a watery mixture.

2. Combine Wet Ingredients: In a medium-sized mixing bowl, add the drained tuna. Then, spoon in the plain Greek yogurt, Dijon mustard, and garlic powder. These ingredients will form the creamy base of your protein mixture.

3. Add Fresh Aromatics: Next, fold in the finely chopped celery and red onion. Ensure they are chopped very small and uniformly so they integrate well into the mixture and provide a pleasant crunch without being overpowering.

4. Introduce Fresh Herbs and Seasoning: Sprinkle in the fresh or dried dill. If using fresh, make sure it’s finely chopped. Season generously with salt and black pepper to taste. Start with a small amount and add more as needed after tasting.

5. Mix Everything Together: Using a fork or a spoon, gently mix all the ingredients until they are well combined. Be careful not to overmix, as this can break down the tuna too much. You want a creamy, yet slightly chunky texture. Taste a small spoonful and adjust seasonings (salt, pepper, dill, or even a touch more mustard) if necessary.

6. Prepare for Serving: Wash and thoroughly dry your butter lettuce or romaine hearts. Separate them into individual leaves, ensuring they are crisp and ready to hold your protein mixture.

7. Assemble Your Snacks: Spoon a generous amount of the protein mixture into each lettuce cup. You can serve them immediately as individual snacks or pack them for later.

8. Optional Salad Addition: If using as a salad topping, simply spoon the mixture directly onto a bed of greens, adding any extra vegetables like cherry tomatoes, cucumber, or bell pepper strips for a complete meal.