Prick the sweet potatoes all over with a fork a few times. Rub with a little olive oil and salt and place on a foil lined baking tray.
Bake until soft, about 50 – 60 minutes, depending on potato size.
Meanwhile, in a small Pyrex bowl mix together the tuna, mayonnaise, celery, thyme, garlic and paprika. Season to taste. Put the fridge until potatoes are baked.
Once the potatoes are baked, split open the top down the length of the potato. Squeeze the ends together to open the potato up a little. Sprinkle ½ of the cheese into each potato. Then spoon ½ of the tuna mixture into each potato. Sprinkle the remaining cheese on top.
Put the filled potatoes back into the oven and bake for about 5 more minutes until the cheese is melted.