Sauté carrots and onions in a large saucepan over medium heat until tender. Add garlic and cook 1 minute longer. Add stock, cover and simmer for 15 minutes. Add tomatoes and cook for an additional 10 minutes.
Purée soup using a hand held blender or in batches using a conventional blender (leave the lid off and cover with a towel when blending hot soup to avoid steam burns). Season to taste with lemon juice, salt, pepper and a small amount of sugar to balance the acidity.
For the grilled cheese croutons:
Sandwich one slice of vegan cheese between two slices of Squirrelly Bread. Butter the outside surfaces of each sandwich with non-dairy buttery spread, and place in a frying pan, cast iron skillet, or griddle over medium heat. Cook on each side until bread is golden brown, and cheese is melted.
Allow to cool for a few minutes before slicing each grilled cheese sandwich into ½ - to 1-inch square croutons.
To Serve:
Ladle tomato soup into individual bowls and top with grilled cheese croutons.