Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Slice the Roma tomatoes and yellow onion into halves and place them on the baking sheet along with the unpeeled garlic cloves.
Drizzle the vegetables with olive oil and sprinkle with sea salt, black pepper, and dried oregano, tossing gently to coat.
Roast the vegetables for 30 to 35 minutes until the tomatoes are soft and slightly charred around the edges.
While the vegetables roast, season the chicken breast with a pinch of salt and pepper, then grill in a non-stick skillet over medium heat for 6-7 minutes per side until cooked through.
Remove the chicken from the heat, let it rest for 5 minutes, then slice it into thin, succulent strips.
Once the vegetables are finished, carefully squeeze the roasted garlic out of its skin and into a high-speed blender.
Add the roasted tomatoes, onion, vegetable broth, and fresh basil to the blender and process until the soup is completely smooth and creamy.
Pour the hot soup into a bowl and top with the grilled chicken strips to serve.