Slice the onion and sauté it with olive oil for 5 minutes until slightly brown. Add the spinach and mix gently with the onion and season with salt, pepper and the nutmeg. It will take very short time until the spinach will “fall” and lose its liquids (less than a minute), then remove from the pan. The spinach will be a great complement to the chicken breasts.
Now to the chicken: salt and pepper the chicken breasts and sear them over high heat for 5 minutes on each side on a not stick iron pan (one that can get inside an oven).
Slice the tomatoes as thin as possible; I (carefully!) use the mandolin for that. Cover each of the chicken breast with 2 layers of the thinly sliced tomatoes and season with salt, pepper and the dried oregano.
Put the pan with the covered chicken breasts in an oven preheated to 400F. After 8 minutes, switch to a broil mode for additional 2-3 minutes. That’s it – the chicken is ready.
I had some tomatoes slices left, so I mixed them gently with some olive oil and salt. It was a great to have the tomatoes in two versions on the plate. Loved it.