Crispy golden potatoes with peppers and onions

Ingredients

• 4 medium russet potatoes, peeled and diced (about 4 cups)
• 1 medium yellow onion, diced
• 1 red bell pepper, diced
• 1 green bell pepper, diced
• 2 cloves garlic, minced
• 1 ½ teaspoons kosher salt
• ½ teaspoon freshly ground black pepper
• ½ teaspoon smoked paprika (optional)
• ¼ teaspoon cayenne pepper (optional)
• 3 tablespoons vegetable oil (or canola oil)
• 1 tablespoon unsalted butter