Preparation

• Melt the butter in a 10-inch nonstick skillet over medium heat. In a small bowl, whisk the eggs with a pinch of salt, then pour into the skillet. Cook, stirring constantly with a silicone spatula, until the eggs are set, about 2 minutes. Remove from the heat.
• In another small bowl, crumble the queso fresco and mix with cilantro. In another small bowl mash the avocado with the lime juice and a pinch of salt. Spread the cheese mixture on the bottom halves of the buns and the mashed avocado on the top halves.
• Divide the eggs between the two buns, season with salt and pepper, and top each with the tomato and onion. Add a dash of hot sauce, if using, then close the sandwiches and serve.