For the Avocado Sauce, combine the avocado, sour cream, cilantro, lemon juice, sugar, salt and pepper in a food processor. Process until smooth. Chill, covered, until serving time.
For the crab cakes, reserve half the bell peppers and half the scallions for the garnish. Combine the remaining bell peppers, remaining scallions, cilantro, crab meat, salt, pepper, thyme and Tabasco sauce in a bowl and mix gently. Stir in the mayonnaise. Add the bread crumbs and toss lightly.
Shape the mixture into 3 inch patties. Handle the mixture gently, as it should barely adhere. Sauté the crab cakes in a nonstick skillet over medium heat for 3 to 5 minutes or until golden brown on both sides.
Puddle some of the Avocado Sauce in the center of each serving plate. Arrange 1 crab cake on each plate. Sprinkle with the reserved bell peppers and reserved scallions. Serve immediately.