Preheat your oven to 400°F and line a large baking sheet with parchment paper.
Slice the Roma tomatoes and yellow onion into halves and place them on the sheet along with the peeled garlic cloves.
Drizzle 0.5 tbsp of olive oil over the vegetables and sprinkle with 0.25 tsp of the sea salt, 0.25 tsp of the black pepper, and 0.25 tsp of the oregano.
Roast the vegetables for 35 to 40 minutes until the tomato skins are slightly charred and the onions are translucent.
While the vegetables roast, season the chicken breast with the remaining sea salt, black pepper, and oregano and sear in a pan with the remaining 0.5 tbsp of olive oil until the internal temperature reaches 165°F.
Slice the cooked chicken into thin strips and set aside.
Transfer the roasted vegetables and all their juices into a high-speed blender, adding the basil and vegetable broth.
Blend on high until the soup reaches a velvety consistency, then pour into a bowl and top with the sliced chicken and parmesan cheese.