Preheat the oven to 400˚ F. Combine the tomato halves, ¼ cup of olive oil, salt and pepper in a large bowl; toss well to combine. Spread the tomato halves out on a large baking sheet. Roast the tomatoes for 45 minutes.
In a large stockpot or Dutch oven over medium heat, combine the remaining 2 tablespoons of olive oil with the butter and heat until the butter is melted. Add the onions, garlic and red pepper flakes to the pot and cook, stirring occasionally, until slightly soften, about 7-10 minutes. Add in the canned tomatoes, roasted tomatoes, basil, thyme and chicken stock. Bring the mixture to a boil. Lower the heat and simmer, uncovered, 40 minutes.
Use an immersion blender to puree the soup until completely smooth. (Alternatively, you can use a blender or food processor. If you do, be sure to vent the steam and be very careful not to spill the hot liquid!)
