Spread the bean pesto over the bottom of a 10inch round glass baking dish. Cover it with the guacamole.
In a small bowl, combine the sour cream, garlic powder, chili powder, cumin, salt, and pepper. Mix thoroughly, and spread on top of guacamole.
Sprinkle the top with the cheese, tomatoes, olives, and scallions. Serve either chilled or hot (bake for 15 minutes in a preheated 425°F oven), with taco chips.