Choose your substitute based on what you have: tomato paste for depth, bouillon for saltiness, and a thin-to-soup texture adjustment for body.
Mix using the listed ratio, starting with less liquid if your substitute is thick (sauce/peppers/ketchup), then add water to match broth thickness.
Taste and correct: add a pinch of salt for saltiness, and a tiny splash of vinegar/lemon if the tomato tastes flat or overly sweet.
Let it sit 2–3 minutes before using so paste/powders fully dissolve and flavors meld.