Preheat oven to 400 degrees. Place tortillas on a baking sheet and bake for 10-15 minutes or until crispy.
While tortillas are baking, drain and rinse black beans. Mash black beans with cumin in a bowl until most beans are smashed and mixture is creamy. Slice avocado, dice tomato, chop green onions and finely chop cilantro.
Remove tortillas from the oven. Spread 1/4 amount of smashed black beans onto each tortilla. Sprinkle with about 2 tablespoons of cheese. Return to oven and bake for 5 more minutes, or until cheese is melted.
Heat a large skillet over high heat and spray with cooking oil. Crack eggs into skillet and fry until white is set, but yolk is still creamy.
Put one fried egg on top of black beans on each tostada.
Top tostadas with fresh tomato, green onion, cilantro and avocado.