Slice off a very thin strip off the bottom of each pepper half so that the cut side is up. (This will allow the pepper to lie flat while you stuff it. Be careful not to take too much off or the mixture will spill out.) In a small bowl, mix Hummus, tomatoes, and olives. Place about 2 tablespoons of the Hummus mixture into each pepper half. Top with diced avocado and sunflower seeds. Serve.