In a large bowl, combine tomatoes, garlic, herbs, capsicum, cucumber, onion, if using, and lemon zest. Season with pepper, sprinkle with 2 tablespoons of lemon juice and mix well to coat.
Divide mixture between 2 plastic containers. Seal with an airtight lid and refrigerate overnight.
When ready to eat at work, dice avocado and add to mix. Toast bread in toaster or preheated grill. Spread toast with refried beans. Top with bruschetta mix and serve.