Combine tomatoes, onion, water, mustard seed, mustard powder, garlic, bay leaf, and black pepper in a large, heavy pot over medium heat; bring to a simmer and cook for 10 minutes. Stir soy sauce through the tomato mixture; continue cooking another 5 minutes. Season with salt. Remove bay leaf to serve.
Tips & Tricks
How to Prepare Fresh Tomatoes
See how to prepare fresh tomatoes for salads, salsas, and sauces.
How to Peel, Seed, and Dice Tomatoes
Watch how to peel, seed, and dice fresh tomatoes for salsas, salads, and more.