First, blend the olive oil, lemon juice, onion, garlic and mustard powder in a blender;

Once the mixture is homogeneous, place it in a bowl and add the piece of meat in such a way that it

stay "immersed" in the mixture;

Cover and refrigerate;

Leave in the fridge for at least 8 hours;

Remove the container and leave it out of the refrigerator for half an hour;

Now transfer the meat to a frying pan and grill (three minutes each side);

Transfer the meat to a greased or parchment-lined baking sheet;

Place in the oven and bake for about 10 minutes (preheat the oven beforehand);

Remove the meat from the oven, let it cool and cut it into thin slices;

In another bowl, add the other ingredients (peppers, coriander, rocket, avocado, tomatoes, watercress and

mayonnaise);

Add a tablespoon of water and stir well;

Finally, add the sliced meat and mix until all the ingredients are well distributed