Combine chopped tomatoes, tomatillos, jalapeños, and garlic in a saucepan. Bring to a boil (tomatoes provide the liquid), reduce heat and simmer 10 to 15 minutes.
Remove from heat and let cool slightly.
Place tomato mixture with the avocados, cilantro and salt in food processor or blender and blend until smooth.
Pour into a bowl and stir in sour cream.
