Crush the chickpeas in a bowl with a fork. Don't mash them completely. Season with salt and pepper.
Add the chopped celery, diced red onion, and green onion.
In a blender, combine the vegan mayo, water, vinegar, flaxseed oil, and garlic and pulse until creamy. Season with salt and pepper.
Add 3 tbsp of the blended dressing to the chickpeas and mix well.
Toast the bread, spread some of the remaining dressing on it, then top with the "tuna" and halved cherry tomatoes.
Enjoy!
Notes
Store the faux tuna salad in an airtight container in the fridge for up to 3 days. Assemble the sandwiches just before serving so the bread stays crisp.