Cover frozen greens with water and bring to boil for 3 minutes. Reduce heat, cover and simmer for 30 minutes
Drain tomatoes, reserving 1/4 cup of the tomato juice. In a sauce pan, saute onions in butter until slightly softened. Add the remaining ingredients to the onions and bring to boil. Reduce heat and simmer for 30 minutes Serve hot tomato salsa over greens.