For the salsa Scoop the onion into a strainer and rinse under cold water. Shake off as much water as possible, then transfer to a small bowl and stir in the tomatoes and lime juice. Add the cilantro and season with salt, usually about 1/2 teaspoon, and it's ready.
For the eggs Beat the eggs with salt, just enough to combine the whites and yolks. Add them to the skillet and scramble until they are as done as you like. Taste for salt, then scoop them into warm corn tortillas, garnish with cilantro and serve right away with the salsa.