In a large sauté pan, sauté onion over medium-high heat 5 to 10 minutes, or until dark brown and caramelized. Add scallions and garlic; continue to sauté for 1 minute more, until softened.
Add corned beef and stir to combine.
Divide hash between 8 latkes, top with spicy ketchup and another latke.
Spicy Ketchup:
In a small bowl, combine ketchup, hot sauce, and pepper. Mix together and dollop on the latke.