1. Cut a lid on top of each tomato. Empty the flesh of the tomatoes with a small spoon and chop. Turn the tomatoes over on paper and set aside.

2. Season the inside of the tomatoes with salt. Chop the shallots and basil together.

3. In a bowl, whisk together the salt and vinegar. Add the mustard and a little pepper. Whisking, incorporate the olive oil in a thin stream.

4. Season the chopped tomato flesh with salt and pepper. Mix with the shallots and basil. Mix with half of the vinaigrette. Reserve the remaining vinaigrette.

5. Cut the black olives into small pieces and the white onions into thin slices.

6. Fill each tomato with the tomato and basil mixture. Sprinkle with olive and onion pieces on top. Drizzle each tomato with the remaining vinaigrette. Serve with fresh bread.