To make the guacamole: In a large bowl, using a potato masher, mash the avocados. Stir in the salsa, garlic salt, and onion powder. Season generously with the seasoned salt and pepper.
Level out the guacamole in a bowl, then squeeze lemon on top to prevent browning.
Spread the sour cream on top evenly. Spread the sour cream evenly over the guacamole, then add a layer of grated cheese.
Sprinkle the olives in a band around the perimeter of the guacamole, then a band of the tomatoes, and finish with the scallions.
Serve chilled with the tortilla chips.