Combine the sourdough bread crumbs and Dungeness crab meat, set aside. Combine remaining ingredients, except olive oil, and mix thoroughly. Gently fold in the crab and bread crumb mixture. Shape into patties approximately 1/2-inch thick. Heat olive oil in a non-stick saute pan. Cook crab cakes over medium heat to a golden brown about 2 to 3 minutes. Set aside.
Combine all ingredients except flower confetti and refrigerate.
Whisk together all ingredients and refrigerate.
Place 1/4 cup of the salad mixture in the center of each of 4 plates. Place a crab cake on top of each salad. Drizzle each plate with Tarragon Vinaigrette and sprinkle with a garnish of flower petal confetti.