Preheat the oven to 450. Wash & slice bell peppers so that you can lay them out on a foil-lined baking sheet. Brush with a small amount of avocado oil and roast for 10-20 minutes (this will depend on your oven) until slightly charred. You can also char them over an open flame if that’s an option.
Remove red bell peppers and once slightly cooled, slice the strips into chunks. This is all going to be blended, so it doesn’t need to be perfect.
Carefully slice the white parts of your leek into rings and rinse them in a colander (leeks hold a lot of dirt in between their layers). Set aside to dry.
Roughly mince garlic and shallot.
Heat a large pot over medium heat. Add a tablespoon of oil to the pot and allow to heat for another minute. Sauté the leeks and shallot until softened, about 5 minutes, stirring frequently.
Add the minced garlic and tomato paste and sauté for another 30 seconds.
Add the canned tomatoes, chopped red bell peppers, broth, coconut milk, seasonings, balsamic vinegar and coconut sugar. Bring to a boil, turn to medium-low and simmer for 30 minutes covered, stirring occasionally.
Using an immersion blender (or transfer soup to a blender in batches), blend the soup to desired consistency. Taste for seasoning adjustments.
To make the grilled cheese, smear two slices of sourdough bread with butter on the sides that will touch the pan. On the other side, spread a bit of pesto. Layer slices of cheese and build the sandwiches.
Heat a skillet over medium heat and melt a tablespoon of butter. Add the sandwiches to the pan and cook until golden brown on one side.
Flip the sandwiches and cook on the other side until golden brown. Turn heat down slightly and cover with a lid if needed to melt the cheese.
Serve soup with a pesto swirl and sliced pesto grilled cheese croutons on top.