If using fresh nopales, make sure all spines and thick edges are removed, then dice them evenly. Bring the water to a boil with the salt, rough onion, and smashed garlic. Add the diced nopales and simmer 10–12 minutes, until tender and their slime has released into the water. Drain well and rinse briefly under warm water to remove excess mucilage. Let them sit in the colander until well drained. The key here is not to leave the nopales wet. They should be tender and clean-tasting, not slippery and waterlogged. Boiling the nopales directly in the water is what draws out most of their natural mucilage into the surrounding liquid rather than leaving it clinging to the paddles — the brief rinse afterward finishes removing what's left, which is exactly why both steps matter together rather than either alone.

Crack the eggs into a bowl and beat until fully combined. Add a small pinch of salt and a few grinds of black pepper. Set aside. Beating only until combined, rather than whipping vigorously, incorporates the seasoning fully without introducing excess air that could affect the finished texture.

Heat the oil or lard in a large skillet over medium heat. Add the diced onion and cook 3–4 minutes until softened. Add the diced chile and cook 1 minute more. Add the tomato and cook 3–4 minutes until it softens and most of its excess moisture cooks off. The mixture should look juicy but not watery. Building this base in stages — onion first, chile briefly after, tomato only once those earlier aromatics are established — lets each component reach its own proper point before the next joins, rather than everything cooking together at a single, less controlled pace.

Add the drained nopales to the skillet and cook 3–4 minutes, stirring regularly, until any remaining moisture evaporates and the mixture tastes concentrated rather than wet. This is an important turning point: if the nopales are still releasing liquid at this stage, keep cooking a little longer before adding the eggs. Even after draining, nopales can still release a little additional moisture once they hit the hot pan — this second cooking stage exists specifically to catch and cook off whatever moisture the earlier drain didn't fully address, protecting the eggs from that final bit of dilution.

Lower the heat to medium-low. Pour in the beaten eggs and gently fold and stir until softly set and creamy. Add the chopped cilantro in the last 30 seconds of cooking. Remove from the heat while the eggs are still slightly glossy, as they will continue setting from residual heat. Taste and adjust salt if needed. Gentle folding, rather than constant vigorous stirring, produces larger, softer curds that stay moist — a genuinely important distinction here, since this dish's whole appeal depends on real contrast between soft eggs and tender, clean-tasting nopales.

Warm the refried beans separately. Warm the tortillas on a dry skillet or directly over a flame until soft and pliable. Divide the nopales con huevo among 4 plates. Serve with a portion of refried beans, crumbled queso fresco over the beans or eggs, and 2 warm tortillas per serving. Warming each side component in its own pan, separately from the main scramble, keeps every part of the plate at its own proper temperature and texture right up until everything comes together on the plate.