You are serving yourself pasta and you have zero access to tomato sauce. All you have in your pantry is ketchup (catsup.) Would you eat the plain pasta, or add ketchup for flavor?
You have NO ACCESS to tomato sauce. You cannot leave to buy any, you cannot call a friend to bring you any, you cannot order any, you cannot make your own sauce, and any other bizarre loophole. It is what it is. What do you do?
There are lots of other sauces you can make. Carbonara, alfredo, lemon garlic, even just butter and maybe a little Parmesan cheese would be excellent.
But ketchup would be interesting, as an experiment.