Cream of tomato-cilantro soup

1 medium onion, diced
1 T butter
14.5-oz can finely diced tomatoes
2 C chicken stock or 2 C water and 2 tsp chicken base
1 bunch of cilantro, finely minced
3 cloves garlic, minced or crushed
1/2 C half and half

Saute the onion in the butter until soft. Add the tomatoes and chicken stock, cover, and simmer for about 15 minutes. Stir in the cilantro and garlic and simmer for 5 more minutes. Remove from heat and stir in the half and half before serving.