Wash the octopus very well to remove the sand and cut the tentacles from the head. We place a piece of aluminum foil on the counter and we put a piece of paper on top, place the four tentacles on.
Slice an onion and put it on the octopus. Add a little garlic, 3 bay leaves, a little thyme and a few grains of pepper. Cover very well and close tightly so that the liquids do not spill into the oven. We do the same with the other tentacles.
Bake at 200 degrees for 1 hour.
Remove from the oven and carefully open the foil because it is really hot. Allow to cool and cut into slices. Put them in a bowl and add olive oil, oregano, lemon and vinegar. Put it in the refrigerator and serve after 1 hour.