Add the tuna and its oil to the bowl of a food processor. Zest the skin of the lemon, and it's juice, add both plus the butter, olive oil, oregano and garlic too. Process all until smooth and creamy. Taste for seasoning, you may want to add salt, pepper or more lemon juice.
Refrigerate it for a couple of hours before serving, if you have time, to allow the flavors to come together. Serve it at room temperature with crunchy vegetables and/or crackers.