Line a roasting pan with parchment paper, now arrange the chopped bell peppers and tomatoes on the pan before coating with 2 tablespoon of olive oil
Proceed to roast in the oven for 20-25 minutes or until slightly charred..
In a medium sized saucepan pour in the other 2tbsp of oil then begin to saute the garlic and onions until translucent on medium heat
Add the carrots and celery to the saucepan, cook for a further 2-3 minutes, be sure to stir and season the veggies with the pink salt and black pepper throughout the given time.
Pour the stock into the pan along with the roasted tomatoes and bell peppers.
Transfer the contents of the saucepan into a blender (or use an immersion stick) with the fresh basil leaves or dried basil, then blend until smooth.
Return to the pan to heat (unless using a machine like the Vitamix which heats the soup) then serve accordingly
Notes
Roasting the tomatoes and red peppers are key to imparting the full flavour of the veggies, albeit this may lengthen the actually cooking process (not by too much).
However, I do strongly suggest roasting the vegetables to experience the depth of flavour in its entirety.