Place tomatoes and garlic on a sheet pan, drizzle olive oil and sprinkle kosher salt on top, then roast on 400F for 30 min
15 minutes before the tomatoes are done, melt the butter in a large pot, add onions and sprinkle kosher salt. Begin to soften the onions on medium heat, once translucent, add thyme leaves, lower flame to medium low and cover the pot allowing the onion to caramelize
Remove tomatoes and garlic from the oven, remove garlic peel and discard, and add everything to the pot. Stir in tomato paste Allow to simmer together for about 10 minutes until tomatoes have mostly broken down
Pour in vegetable stock, add other half stick of butter, sugar, and raise heat and bring to a boil, then lower flame and let simmer on medium-low for 40 minutes.
Blend well with an immersion blender or in a stand blender (this step will be easier if the soup is allowed to cool for a bit first, but its not necessary)
Pour and stir in heavy cream slowly until desired creaminess is reached (start with half cup and go from there, READ RECIPE NOTE!!) and add salt to taste, simmer for another 10 minutes and serve hot!