Preheat oven to 425.
Cut Roma, cherry, or any large tomatoes in halves or fourths and place them on a large baking sheet.
Slice onions into half-inch thick slices. Place on a baking sheet with tomatoes. If using whole garlic, add garlic to the baking sheet as well.
Brush onions, tomatoes, and whole garlic with olive oil. If you are using minced garlic, after brushing tomatoes and onions with olive oil, sprinkle minced garlic over an entire pan of cut tomatoes and onions.
Salt and pepper the entire pan. Roast tomatoes and onions for 35-40 minutes. Well-done edges are fine, but don't let onions burn. If they are getting too done, they may need to remove onions a few minutes early.
Remove tomato peels if desired; I don't since they are going to be pureed anyway. I prefer to leave the skin on when I use organic fruit and vegetables.
Place roasted onions, tomatoes, garlic, and basil leaves in a food processor; I use my Vitamix. Puree well.
Add pureed mixture to broth in a large kettle. Bring mixture to a boil and then simmer for about 20 minutes. Add more or less broth depending on desired consistency. Additional salt and pepper as desired.
Serve some up and enjoy that hearty flavor. Leftovers can be frozen and come in handy on a busy weeknight.