Preheat oven to 400℉
Wash tomatoes and remove stems from the tomatoes and put them in a bowl. Toss with olive oil and place on a parchment-lined baking sheet.
Roast for 25-30 minutes or until the tomatoes burst. Remove from oven and set aside.
Add the olive oil to a heavy-bottomed dutch oven. Add the onions and cook til they start to become translucent - about 5 minutes.
Add garlic, herbs, and red pepper flakes and stir for 1 minute.
Add tomatoes and all the cooking liquid and simmer for 25-30 minutes, occasionally stirring.
Remove from heat and cool for 15 minutes.
Use an immersion blender or blender to blend to your desired consistency.
Add salt and pepper to taste.