1 tablespoon ketchup
1/2 cup white wine vinegar
1/2 cup cider vinegar
1/2 cup house-made mustard
1/4 teaspoon salt
1/8 teaspoon crushed red pepper flakes
In a small bowl, mix ketchup, vinegar, tomato paste, and salt. Mix well, cover saucepan, and allow to sit overnight.
In the morning, in a small saucepan, bring vinegar, ketchup, mustard, salt and pepper flakes to a boil. Remove from heat, and let cool to room temperature. Pour sauce over vegetables.