Cut away any blemishes and stems and puree the tomatoes in the blender a few at a time.
15 tomatoes
Add the onion and garlic and blend until smooth.
1 small onion, 6 cloves of garlic
Pour puree into a pot.
Bring to a boil adding ¼ teaspoon of salt at a time until seasoned the way you like it.
About ½ teaspoon kosher salt
Once boiling, lower and simmer for about ½ an hour. I served mine with a bit if feta and a sprinkle of parsley. Made it look pretty.
The soup will get thicker and thicker the longer you simmer. Add water to get to your desired consistency. I like mind fairly think so it sticks to the grilled cheese.