Wash and prepare all vegetables.
In a large bowl, combine cabbage, carrots, cucumber, bell peppers, tomatoes, and onion.
In a small pan, heat oil and add mustard seeds until they start to pop.
Remove from heat and let cool slightly.
Pour the mustard seed oil over the vegetable mix.
Add lemon juice and salt to the bowl.
Toss everything together until well combined.
Let the salad sit for 10 minutes to allow flavors to meld.
Serve chilled or at room temperature.
Garnish with fresh coriander if desired.