INGREDIENTS
1
large onion (, finely chopped (about 1 1/2 cups))
2 tsp
butter
Kosher salt
2 tbsp
plus 2 teaspoons mayonnaise
1 tbsp
ketchup
2 tsp
sweet pickle relish
1/2 tsp
sugar
1/2 tsp
distilled white vinegar
4
slices deli-cut American Cheese
2
lbs russet potatoes (, peeled and cut into 1/4 inch fries)