Preheat your oven to 400°F and line a large baking sheet with parchment paper.
Halve the Roma tomatoes and the yellow 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 to 30 minutes until they are soft and slightly caramelized around the edges.
While the vegetables roast, season the chicken breast and grill it in a pan over medium heat until cooked through, then slice into thin strips.
Transfer the roasted tomatoes, onion, and garlic into a high-speed blender, ensuring you include any juices from the pan.
Add the rinsed cannellini beans, vegetable broth, and fresh basil leaves to the blender.
Blend on high speed until the soup reaches a completely smooth and velvety consistency.
Pour the soup into a bowl and top with the sliced grilled chicken strips to serve.