HOW TO PREPARE
Mix valentina, maggi, soy and lime juice and place over thinly cut sliced tuna to marinate for about 30 minutes. Mix cream cheese and mayo until incorporated and then add avocado, serrano mix together. Season well with salt.
Fry red onion into crispy over low heat in a small frying pan, for about 3 minutes. On the tostada spread a layer of the avocado mix. Then top with marinated tuna, top with a cloud of red onions and serve.