Mince the onion. Wrap tofu in kitchen paper and let it drain for 10 minutes, then cut into 1.5cm cubes. Cut spinach into 4cm pieces and microwave for 2 minutes at 600W.

Heat olive oil, grated garlic, and minced onion in a frying pan over medium heat until the onion softens.

Add tuna and diced tomatoes to the pan and simmer over medium heat for about 5 minutes. Season with sake, salt, and pepper.

Layer tofu in a heatproof dish, season with salt and pepper, then add spinach and tomato sauce in order.