Begin by carefully slicing each avocado in half lengthwise and remove the pits. Scoop out a small portion of the flesh to create more space for the filling.

In a bowl, combine drained tuna, red onion, and celery. Add reserved avocado flesh and mash gently to create a creamy mixture.

To the mixture, add mayonnaise, lemon juice, and Dijon mustard. Stir until well combined, adjusting seasoning with salt, pepper, and paprika.

Fill each avocado half with the tuna mixture, packing it in well for a satisfying presentation.

Optionally sprinkle fresh herbs and smoked paprika over the top before serving.