Place a heavy bottom pan over medium heat.
Add the oil and onions to the pan and cook for 5 - 8 minutes until onions are tender and translucent.
Meanwhile, roughly chop the fresh thyme and place in a small coffee grinder with the salt. Blend until it forms into a salt consistency again (if you don’t have a coffee grinder, you can pick the thyme and roughly chop the leaves).
Add this to the onions and simmer for 3 - 4 minutes.
Add puréed garlic to the pan and cook for an additional 5 - 8 minutes.
Roughly chop the canned tomatoes and add these (including the juice) to the onions. Simmer for 30 minutes.
Add the white wine and sherry. Simmer for 20 minutes.
Pour into a Vitamix or blender and blitz for 10 seconds on high speed.