In Jain Dharma, tomato itself is generally allowed, because:

• Tomato is a fruit / above‑ground vegetable, not a root (kand-mool).
• Jain rules mainly prohibit meat, eggs and root vegetables like potato, onion, garlic, carrot, beet, etc.

So plain tomato or tomato-based sabzi (without onion, garlic, etc.) is normally acceptable in both Śvetāmbara and Digambara household practice.

For tomato sauce / ketchup, check these points:

1. Must be strictly vegetarian – no egg, no fish sauce, no animal products.
2. No onion–garlic or other root extracts in ingredients (many market sauces contain onion/garlic powder, “natural flavour”, etc.).
3. No alcohol / wine vinegar if you also avoid such items.
4. Prefer freshly made sauce at home (same‑day use), as Jain dharma discourages eating foods stored long or heavily fermented.

So:

• Homemade tomato sauce from tomato, permissible spices and salt – generally allowed.
• Market tomato sauce – read the label carefully; if it has onion/garlic or other non‑Jain ingredients, it should be avoided.

If you want a simple list of Jain food basics, you can read more here