Like so many authentic Basque dishes, Marmitako pulls so much rich flavor from just a few simple ingredients. If you're looking for an easy one pot meal (that's also gluten-free and dairy-free), this Spanish tuna stew with onion, peppers, and potatoes is one of my favorites that I learned on my travels in the region. To save time, you can pulse the onion, peppers, and garlic in a food processor to finely chop.