Leftover Corned Beef Reubens - Sprinkles & Sea Salt

Ingredients

• 2 tbsp unsalted butter
• 1 large onion, sliced thin
• 1 tsp salt
• 1/2 cup sauerkraut (drained)
• 2 tbsp sweet pickle relish
• 1 tbsp ketchup
• 2 tbsp mayonaise
• 1 tsp Worcestershire sauce
• pinch of salt
• 1 pound leftover corned beef
• 4 slices swiss cheese
• 6 slices marbled rye bread
• caramelized onions
• sauce