Melt butter in a large stock pot over medium heat. Add the chopped onion, carrot, celery and garlic. Cook, stirring regularly, 5 minutes or until vegetables are tender and starting to brown.
Sprinkle the flour over the vegetables and stir over low heat for 1 minute, until the flour is fully incorporated.
Add the chicken broth, tomatoes, red peppers, tomato paste and sugar. Bring to a boil. Reduce heat to medium-low; simmer 15-20 minutes until vegetables are tender.
Use an immersion blender or transfer the soup to a blender and blend until smooth.
If using a blender, return the soup to the pot. Stir in the half & half; season with salt and pepper and heat through.
Garnish with grilled cheese croutons, fresh Parmesan, and fresh parsley or basil as desired.