MOP SAUCE INGREDIENTS
(makes about 2 cups)

2 cups distilled white vinegar
1 tablespoon coarse salt
1 teaspoon black pepper, or more to taste
1 teaspoon hot red pepper flakes, or more to taste
1 small onion, thinly sliced
1 jalapeño pepper, thinly sliced

Combine vinegar, salt, black pepper, and hot pepper flakes in a glass bowl and whisk until the salt dissolves. Stir in the onion and jalapeño. This sauce can be made a few hours in advance but use it the same day.