Whisk together 1 Tbsp. light brown sugar, 2 tsp. kosher salt, 1 tsp. paprika, 1/2 tsp. dry mustard, 1/2 tsp. dried oregano, 1/2 tsp. freshly ground black pepper, 1/4 tsp. granulated garlic, 1/4 tsp. ground coriander, and 1/4 tsp. onion powder in a bowl. Whisk in 1/2 cup mayonnaise and 1/4 cup apple cider vinegar until sugar dissolves. Cut 1/2 head cabbage (about 1 lb.) into thick slices; cut slices crosswise. Fold cabbage, 1 cup diced green bell pepper, and 1 cup diced red onion into mayonnaise mixture until coated. Let stand 1 hour before serving, tossing occasionally.