Okay, for the 5 cups of heirloom tomatoes, you don’t need all of them to be green. But you probably want most of them to be green and yellow as red and darker tomatoes will make this soup look funky. But that only matters if you are into the food aesthetic. If not, use whatever tomatoes you have on hand.
Run the 5 cups through the food processor, until super smooth. Transfer it to a large mixing bowl, setting aside 1/2 cup. If you want, you can run this through a sieve to remove the larger chunks but I personally like the texture. Up to you, but don’t do it the wrong way!
Finely chop the 1/4 cup basil, 1/4 cup cilantro, 5 tarragon leaves, 2 cloves garlic, and serrano pepper in the food processor, adding it to the tomato puree.
Halve and pit the 2 avocados, then add them to the food processor, along with the juice of one lime and 1/2 cup of tomato puree. The reason for the tomato puree is that avocados do not blend easily without a little liquid help.
Add the avocado puree to the tomato and herb mixture and mix it well. Then chill it in the fridge for an hour or more.