In a small fry pan or skillet, spray some cooking oil and crumble the feta cheese over it, making sure to cover the outer circle of the pan as well.
Let the feta cheese sizzle over medium heat for a few minutes until it begins to melt without burning.
Crack the egg in the center of the pan. Season with dried oregano and red pepper flakes. Cook the egg to your preferred doneness.
Warm the tortilla on a gas stove, oven, or microwave. Spread the smashed avocado on the tortilla and add a squeeze of lemon juice.
Once the egg is cooked and the feta has a golden crust, gently remove it from the pan and place it on the tortilla.
Garnish with pickled onions and a drizzle of chili oil.