Cook the egg by heating the butter in a small nonstick skillet over low heat.
Crack the egg into the nonstick skillet, take a knife, and poke some holes in the thicker whites, which breaks the membrane and cooks it fully with the rest of the whites.
Cook over low heat for about 2 minutes, or until the whites are set. Season with sea salt and freshly cracked pepper, to taste. Side Note: Add a teaspoon of water to the nonstick skillet once the egg white sets, to prevent the egg from getting crispy on edges, if desired.
While the egg cooks, heat the tostada shell and the black beans.
Finish by slathering the black beans over the warmed tostada shell then sprinkle the pepper jack cheese and red onions on top.
Finally, add sunny side egg, avocado slices, diced tomato, green onions, and cotija cheese. Serve immediately with salsa, hot sauce, and sour cream. Enjoy.