Place the octopus in a large pot and heat, add a bit of water, the octopus itself will release water. Let it simmer for about 20 minutes. The octopus will shrink and curl.
Remove octopus from pot. Save the octopus water. Cut into small pieces about ¾ of an inch. Set aside.
In another pot sauté the onion until translucent, add the octopus pieces and continue sautéing for a few more minutes. Add the tomatoes, the tomato paste and about 1 1/2 cup water (it can be the octopus water depending on the strength of flavor you like or a mixture) and the wine. Cover and let it simmer for about 40 minutes.
Add the pasta and let it cook for about 12 minutes until pasta is done.
Notes
*You can also cook the pasta separately. Greek dishes tend to cook pasta more and not al dente, so you may wish to cook the pasta al dente separately and then mix it with the sauce. It won’t have as much octopus flavor though, since in the original version the pasta cooks with the octopus.*In the traditional cookbooks they recommend that octopus should not be cooked with salt. I am not sure of the reason, but that is just fine with me as I usually add the salt afterwards in the recipes.