Combine onion, quinoa, bell pepper, Kerrygold Dubliner® Cheese, egg and egg whites, garlic and chili powder, salt and pepper in a medium mixing bowl and mix gently with a spoon or spatula. Heat a large skillet sprayed with cooking spray over medium-high heat. Using a 1/2-cup measuring cup, measure half cup portions of the quinoa mixture and turn out into the pan, flattening each until 1/2-inch thick. Cook for 2 to 3 minutes, or until bottom is browned and the cake is firm. Flip cakes over and cook for an additional 2 minutes. Top each serving with half the chopped avocado and tomato, dividing equally. If serving as individual cakes, top each with 1 tablespoon of chopped avocado and tomato.