Prep the octopus: Bring water and a tbsp of salt to a boil in a large pot. Rinse the octopus with cold water. Once the water comes to a boil, dip the octopus three times in the boiling water. Lower the temperature to a simmer and cook the octopus in water until tender. 

Remove the octopus from the water, place it in an airtight container, and refrigerate for at least two hours (you can also leave it overnight).

Once the octopus is cooled, chop it into 1-inch pieces and set aside. 

Prep the vegetables: The quantity is just a guideline. Use more or less of your preferred ingredients to suit your taste. Dice the peppers, cut the cherry tomatoes into fourths, halve the olives, and cut the red onions into very thin slices. 

In a large bowl, mix all the ingredients, adding olive oil and mixing well. Follow with vinegar, salt, and pepper to taste. Serve with tostones.