These bite-sized tomato salads are a unique, flavorful approach to an appetizer course.
Prepare an ice bath, and bring a large saucepan of water to a boil.
Using a slotted spoon, lower the tomatoes, a few at a time, into the boiling water. Cook 15 to 30 seconds. Transfer tomatoes to the ice bath, and let stand several minutes. Drain the tomatoes in a colander.
Peel the tomatoes; remove and discard the cores. Slice tomatoes in half, and, using a melon baller, remove and discard all the seeds. Cut the tomato flesh into 1/4-inch dice, and transfer to a medium bowl. Sprinkle tomatoes with 1 teaspoon salt, and let them stand about 25 minutes.
Place the tomatoes in a sieve, and gently press down on the flesh, extracting as much of the liquid as possible. If your tomatoes are particularly juicy, let them stand 15 minutes more; reserve tomato water to use in sauces or vinaigrettes. Return the tomato flesh to the bowl, and add olive oil, garlic, shallot, and marjoram. Season with salt and pepper; mix to combine.
Generously brush a 1/2-cup dry measure with olive oil. Fill with tomato mixture, and press down with the back of a spoon, extracting any excess liquid; pour off liquid. Line a salad plate with a shiso leaf. Run a small knife between tomato mixture and the measure, and invert measure on shiso leaf. Gently tap bottom, and unmold salad.
Repeat step five with the remaining tomato mixture and shiso leaves, and serve.
To make these individual salads, use red, yellow, and green tomatoes.