First things first, let's prepare the tuna. Open your can of tuna and drain it thoroughly. You want to ensure there's no excess liquid, as this can make your filling watery. Tip the drained tuna into a medium-sized mixing bowl. Use a fork to gently flake the tuna until it's separated into small, even pieces. You should notice the tuna looking lighter in colour and more crumbly, ready to absorb all those lovely flavours.

Now for the flavour base. To the flaked tuna, add the mayonnaise, fresh lemon juice, Dijon mustard, finely diced red onion, and finely diced celery. This combination forms the creamy, tangy heart of our stuffing. Stir everything together with your fork until all the ingredients are well combined and the mixture has a uniform, pale creamy consistency. Take a moment to appreciate the subtle onion and celery aromas starting to mingle.

Next, we'll season and brighten. Stir in the chopped fresh parsley and the optional pinch of smoked paprika. Season generously with salt and freshly ground black pepper. Give it a good mix and then taste a small spoonful. Adjust the seasoning as needed – perhaps a little more lemon juice for tang, or another grind of pepper for a kick. The mixture should taste balanced, fresh, and vibrant.

Time to get the avocados ready. Carefully slice each avocado in half lengthwise around the seed. Gently twist the halves apart. You should hear a satisfying little 'pop' as they separate, revealing the beautiful green flesh and the large seed. Carefully remove the seed by either scooping it out with a spoon or gently tapping it with the blade of a knife and twisting it out.

To create space for our delicious filling, you'll need to scoop out a little of the avocado flesh from each half. Use a spoon to carefully remove about 1-2 tablespoons from the centre of each avocado half, creating a deeper well. Be gentle so you don't break the avocado skin. You can chop up the scooped-out avocado flesh and stir it into your tuna mixture for an extra creamy texture and even more avocado goodness. The avocado halves should now look like perfect little green boats, ready for filling.

Finally, the assembly! Spoon a generous amount of the tuna mixture into each avocado half, mounding it slightly. The creamy tuna should sit proudly in the vibrant green avocado shell. Garnish with halved cherry tomatoes and a sprinkle of fresh chopped chives for a pop of colour and extra freshness. Serve immediately and enjoy your beautiful, high-protein lunch!