Pickled Onions (optional): Thinly slice a red onion and place into a jar. Add white vinegar, then fill the rest of the jar with water. Add a pinch of salt and sugar, shake well, and refrigerate for 30–60 minutes.

Fry Tortillas: Heat oil in a skillet over medium heat. Fry tortillas 1–2 minutes per side until crispy and golden. Transfer to a paper towel-lined plate and sprinkle with salt.

Fry Eggs: Wipe pan clean. Add a few tablespoons of enchilada sauce to the pan to form little pools. Crack 1 egg into each sauce pool (cook in batches). Cook 4–5 minutes, until whites are set. Sprinkle cheese around edges in the last few minutes for crispy, cheesy edges.

Assemble Tostadas: Layer each tortilla with refried beans, a fried egg, and toppings of choice like pickled onions, avocado, and cilantro. Sprinkle with salt. Serve immediately.