Let me tell you one of my fantasies- to eat an entire tuna, much like a bear eats salmon. Only the fish has no scales or bones or guts and is pretty much 100% sushi-grade tuna. So really, just a big plate of tuna.
Sushi is too much work. Cooking rice might warm up the house. But how about some Spicy Tuna Tartare? 1 tablespoon mayo, 1 teaspoon soy sauce, 1/2 teaspoon hot chili sauce mixed together. Add chopped chives and about a cup of finely diced tuna.