Preheat oven to 500 degrees.
In a small bowl, combine 3/4 cup of broth, the brown sugar, vinegar and soy sauce. Place onion, garlic and tomatoes in a 9- x 13-inch METAL baking pan coated with a little olive oil (NEVER USE GLASSWARE FOR BAKING AT SUCH A HIGH TEMPERATURE!).
Pour broth mixture on top and bake for 50 minutes or until vegetables are lightly browned.
Transfer tomato mixture to a food processor or blender; add remaining broth and half and half; process until smooth.
Strain mixture through a sieve into a bowl; discard solids and season with pepper to taste.