Put the beets on the large grater and mix with salt, pepper, balsamic vinegar, lemon juice and oil, then add the chopped parsley and feta cheese and mix to blend.
Sprinkle salt, pepper and thyme on the piece of steak and cook on a hot grill for a few minutes, often turning it from side to side.
Heat the foccacia in the oven.
Chop the baked peppers and mix with the parsley, salt, pepper, balsamic vinegar and olive oil. Place the piece of steak on top and let it rest for a few minutes.
Cut the focaccia longitudinally, sprinkle with a little olive oil, grease one of the halves with horseradish and place the arugula on top.
Cover the steak with the baked pepper mix, slice it, place it on the focaccia, and pour the rest of the baked pepper mix on top, together with the resulting juice.
It is consumed immediately.