Spiced Mustard Hash Browns

Name: Spiced Mustard Hash Browns
Ingredients: 2 tablespoons canola oil; 1/2 red onion, finely diced; 4 tablespoons (1/2 stick) butter; 5 russet potatoes, peeled, parboiled, and diced; 1 tablespoon kosher salt, plus for the vinaigrette; 2 teaspoons dried Mexican oregano; 1/4 teaspoon ground coriander; 1/4 teaspoon ground cumin; 1/4 teaspoon freshly ground black pepper, plus for the vinaigrette; 3 tablespoons whole-grain Dijon mustard; 3 tablespoons red wine vinegar; 1 to 2 teaspoons honey; 3/4 cup olive oil; 4 scallions, chopped on the diagonal; 1/4 cup chopped fresh cilantro