Core the tomatoes, cut into pieces, and place in a blender. Blend until pureed. Strain through a sieve into a bowl. You should have about 1-1/2 cups puree.

Heat 1 tablespoon of the olive oil in a nonreactive medium saucepan until hot. Add the garlic and sauti briefly until light brown. Add the tomato puree and bring to a boil. Simmer gently about 5 minutes. Strain through a fine-mesh sieve into a bowl. Discard the solids. Rinse out the saucepan, return the tomato juice to the pan, and bring to a boil. Simmer and strain twice more until the tomato juice is as thick as heavy cream, about 15 minutes' total cooking time. Be sure to lower the heat as the mixture thickens to prevent scorching. You should have about 1/4 cup of very smooth tomato juice. Add 1 tablespoon lemon juice and taste for salt and pepper.

Pour 1 tablespoon of the olive oil into a small, clean glass bottle with a stopper and swirl to coat the inside. Strain the tomato juice into the bottle. Let it cool to room temperature. Add 2 tablespoons of the olive oil. Do not shake or mix!

Bring a large pot of water to a boil and add salt. Add the corn and cook just until tender, about 3 minutes. Remove and set aside. Cook the beans in the same water just until tender, about 3 minutes. Drain. If using favas, peel them. When the corn is cool enough to handle, cut the kernels from the cobs. Toss together in a bowl.

In a clean jar with a lid, shake together the vinegar, tarragon, 3 tablespoons of the bacon, and 6 tablespoons of the olive oil. Pour enough of the dressing onto the corn and beans to coat, toss well, and taste for seasoning. Adjust with salt, pepper, and more dressing as necessary. Set aside to marinate for about 15 minutes.

Season the fish on both sides with salt and pepper. Heat the remaining 2 tablespoons olive oil in a large saute pan over medium-high heat until hot. Add the fish and cook until brown on the first side, about 3 minutes. Turn and continue to cook until opaque throughout, about 3 minutes longer. Remove from the pan and keep warm.

When ready to serve, pile the corn mixture on a platter or divide among 4 large plates. Arrange the fish on top of the salads. Shake the tomato vinaigrette bottle gently. You don't want the mixture to emulsify, but to have separate droplets suspended within the oil. Spoon or shake about 1 tablespoon of the "broken" tomato vinaigrette on each piece of halibut and then drizzle or shake more tomato vinaigrette around the edges of the platter or plates. Garnish with the remaining prosciutto bits.