In a medium saucepan, combine the cherry tomatoes with the olive oil, basil leaves, crushed garlic and 1 tablespoon of kosher salt.
Cook over low heat until the tomatoes just start to soften but the skins are still intact, about 20 minutes.
Let the tomatoes cool slightly.Preheat the oven to 350°.
Brush the baguette slices with some of the tomato oil and arrange them on a baking sheet.
Bake for about 8 minutes, until they are lightly browned and just crisp.In a large saucepan, heat 2 tablespoons of the tomato oil until shimmering.
Add the minced garlic, clams and wine and bring to a boil.
Cover and simmer over high heat until the clams open, about 5 minutes.
Discard any clams that do not open.
Add the butter, crushed red pepper and saffron and cook, stirring, until the butter is melted, about 30 seconds.
Stir in the parsley and marjoram.
Ladle the clams and broth into bowls and spoon the tomato confit and some of the oil on top (reserve the remaining oil for later use).
Rub the baguette toasts with the halved plum tomato and sprinkle with fleur de sel.
Serve right away.