Preheat the oven to 180 degrees C. Prepare a small pan about 20 cm in diameter that can be placed in the oven (if necessary, you can wrap the handle with aluminum foil or transfer the filling from the pan to an ovenproof dish).
Blanch the tomato in boiling water, peel off the skin, cut into thicker slices. In a deep plate, thoroughly whisk the eggs with a fork with cream, season with salt.
Heat the butter in a pan, clarify it (skim and discard the foam from the surface). Add finely chopped onion and garlic to the pan, cook until translucent. Add chanterelles, sauté for another about 1 minute.
Pour in the egg mixture, arrange cheese and tomato slices, season with pepper. Fry for about 2 minutes (the mass at the edges should bubble), then place in the oven (uncovered) for 15 minutes. After removing from the oven, sprinkle with fresh thyme and optionally season with additional salt.