Heat a lightly oiled non-stick pan over medium heat and sprinkle crumbled feta in an even layer. Let it cook undisturbed until the cheese begins melting and forming golden, crispy edges underneath.
Gently crack the egg directly onto the feta layer. The egg cooks while absorbing the salty, crispy cheese flavors, creating a delicious crust around the edges.
Sprinkle oregano and red pepper flakes over the egg. Cook until egg whites are fully set and the yolk reaches your preferred consistency, either runny or firm.
While the egg cooks, warm your tortilla or toast. A warm base keeps the dish comforting and prevents the egg from cooling too quickly when served.
Mash avocado and spread it over the warm tortilla or toast. Add a squeeze of lemon juice to enhance flavor and balance the richness of the cheese and egg.
Carefully slide the crispy feta egg onto the prepared base. Add pickled onions, chili oil, or fresh herbs, then serve immediately while hot and crisp.