Heat up a saucepan or saute pan large enough to hold all the tomatoes over medium heat. When hot, add 2 tablespoons of the butter and let it melt.
Add the shallot and cook for a couple of minutes and then add the garlic. Stir and cook for another minute or two until the garlic becomes fragrant but do not let it burn.
Add the tomatoes, season with a little salt and pepper, stir and cook until the tomatoes start to soften. This can take anywhere from 5 to 10 minutes depending on you stove. If they break down more than you expect, don't fear, they will still be great in the sauce.
Add the remaining 2 tablespoons of butter to the pan with the creme fraiche and the chopped tarragon leaves. Stir to combine and cook for a minute or two.
Taste and adjust seasoning with salt and pepper.
Serve with the ravioli or chicken or any other delicious main course.