Slow-Cooker Turkey Breast with Orange and Herbs

Ingredients

• 3 tablespoons unsalted butter, at room temperature
• Zest of 1 orange
• 1 tablespoons chopped fresh thyme, plus sprigs for serving
• 2 teaspoons chopped fresh rosemary, plus sprigs for serving
• 2 teaspoons chopped fresh sage, plus sprigs for serving
• 1 teaspoon garlic powder
• 1 teaspoon smoked paprika
• 2½ to 3 pounds skin-on turkey breast
• Kosher salt and freshly ground black pepper
• 2 small onions, peeled and quartered
• 1 blood orange (or orange), cut into thin rounds, for serving