Sorry hope this not too late for you:
Cook some pasta (any shape or kind) so you end up with about 3 cups.
Make a cheese sauce, for mine I melt about 60g butter and stir in 1/4 cup plain flour, cooking over heat for about a minute before slowly adding about 750ml milk stirring the whole time until thick.
Chop up whatever vegies you have around - I usually grate some carrot, zucchini, onion & capsicum and simmer in the sauce for about a minute.
Take sauce off heat and mix through 1 cup grated cheddar cheese, cooked pasta, tuna (I use 2 tins) and then place it all in a baking dish.
Top with some breadcrumbs and more grated cheese then bake for about 25mins at around 200C.
You can use whatever you have in the fridge/cupboard for this recipe and I try to make it a bit healthier for hubby & I by using wholemeal pasta, adding as much vege as can, tuna in mineral water rather than oil and minimising cheese as much as possible.
Enjoy!