Make a crispy tostada by heating a small skillet over medium heat. Coat both sides of the corn tortilla with cooking spray.
Place the tortilla in the hot skillet, pressing it flat, and cook for 3-4 minutes on each side, until golden brown and crisp. Remove it from the skillet and place it on a paper towel to drain.
Cook the poached egg by filling a small saucepan with a few inches of water and the vinegar.
Break 1 egg into a small bowl.
Once the water is at a simmer, stir the water with the bottom of your slotted spoon, clockwise to create a swirling motion in the water.
Quickly slide the egg into swirling water. Cover and turn the stove off. Poach until whites are firm and yolks are still runny, 3 minutes and 30-45 seconds.
Meanwhile, reheat the refried beans and steak in the microwave.
Create the breakfast tostada by placing the crispy tortilla on a plate, then layer with the refried beans, cheese, steak, tomatoes, green onions, and avocado slices.
Using a slotted spoon, remove the egg and drain it over the pan.
Add the poached egg to the top of the tostada, then season with sea salt and freshly cracked pepper, to taste.
Sprinkle the cilantro over the egg and serve immediately. Enjoy.