Preheat your oven to 400°F and line a large baking sheet with parchment paper.
Halve the Roma tomatoes and roughly chop the onion, then place them on the baking sheet along with the whole garlic cloves.
Drizzle the vegetables with olive oil and sprinkle with sea salt and black pepper, tossing to coat evenly.
Roast the vegetables for 25-30 minutes until the tomatoes are blistered and the onions are caramelized.
While the vegetables roast, poach or pan-sear the chicken breast until it reaches an internal temperature of 165°F, then shred it finely with two forks.
Transfer the roasted tomatoes, onions, and garlic into a high-speed blender, ensuring you include all the juices from the pan.
Add the chicken bone broth and fresh basil to the blender, then process on high until the mixture is completely smooth and velvety.
Pour the soup into a medium pot over low heat and stir in the Greek yogurt until fully incorporated and creamy.
Fold the shredded chicken into the soup and simmer for 2 minutes to heat through before serving.