Cube the tomatoes and remove excess juice. You can peal them beforehand if you want. Saute the chopped banana shallot for 2 minutes on medium heat with the finely chopped rosemary and finely chopped garlic and season with salt and pepper. It's important to have some caramelisation on the onion. Add the chopped tomatoes and oyster sauce and bring the heat to high and stir for 1 minute. Add the mirin or sweet wine and the sake and evaporate the alcohol. Simmer on medium for 5 minutes. Season with salt and pepper to taste, but not too much since we will add capers at the end.