Pre-heat oven to 170° C (340°F).
Lay tomatoes, capsicum and garlic on a roasting tray and drizzle with olive oil.
Roast for around 20 minutes or until the garlic is soft. Allow to cool slightly.
Remove skin from capsicum.
In a large pot put roasted tomatoes, capsicum, garlic (removed from the skin), celery, fennel, carrots and onion on medium heat.
Add the passata, dijon mustard, worcestershire sauce, sugar, vinegar, tomato paste, celery salt, cinnamon, ginger, sea salt and water and bring the mixrure to a simmer.
Adjust heat to low.
Season lightly with pepper and cook for around 15 minutes or until the vegetables are cooked.
Add tomato concentrate and stir.
Taste and season if needed.
Take off the heat and allow to cool for blending.
In batches (if necessary) blend all ingredients with ground flaxseed. Store in airtight bottle/jar in the fridge or sterilise jars and store in a cool place for up to one month.