Slice the onion thinly and remove the stems from the cherry tomatoes.

Sprinkle sake and salt and pepper over the sea bream fillets and let them sit for 5 minutes.

Heat olive oil in a frying pan over medium heat, add the onion and sauté until golden. Season with salt and pepper, then push to the side of the pan.

Add the sea bream, cherry tomatoes, and lemon juice to the pan. Cover with a lid and steam over low heat for 5 minutes.