2 tablespoons unsalted butter
2 tablespoons olive oil
2 large onions, halved and cut into 1/2-in.-thick slices
1 teaspoon kosher salt
1/2 teaspoon freshly ground black pepper
In a large frying pan over medium heat, melt butter with oil. Add onions. Sprinkle with salt and pepper and cook over low heat, stirring occasionally, until well caramelized, 15 to 20 minutes.
Note: Nutritional analysis is per 2-tbsp. serving.