Preheat your oven to 400°F and line a baking sheet with parchment paper.
Slice the Roma tomatoes and yellow onion into halves and place them on the baking sheet along with the peeled garlic cloves.
Drizzle the vegetables with olive oil and sprinkle with sea salt, black pepper, and dried oregano.
Roast the vegetables for 25-30 minutes until the tomatoes are soft and slightly charred around the edges.
While the vegetables roast, poach the chicken breast in simmering water for 12-15 minutes until fully cooked, then remove and shred with two forks.
Transfer the roasted tomatoes, onion, and garlic into a high-speed blender, ensuring you include any juices from the pan.
Add the chicken bone broth, coconut milk, and fresh basil to the blender and process on high until the mixture is completely silky and smooth.
Pour the blended soup into a medium pot over low heat and stir in the shredded chicken.
Simmer for 5 minutes to allow the flavors to meld, then ladle into a bowl and garnish with extra basil if desired.