sweet potato gratin with red onions

I’ve had this deep desire to start making cozy recipes for the holidays the last few weeks and this was the first one that came to mind. I’ve seen gratin recipes over and over again in cookbooks and on restaurant menus however they always seem to include some sort of cheese and breadcrumbs, which makes them out of my league, if you know what I mean.

The better I feel, the more I want to shift out of my comfort zone of cooking and start exploring recipes that would have otherwise intimidated me – and which I did not even have the slightest bit of energy to make or explore. That said, this gratin was a huge step for me and it makes me so happy to see that my creative spark is reemerging in the kitchen.

This recipe is perfect for a holiday dinner party or as one of the side dishes on your holiday table. It’s easy to make and requires a mandoline, which I highly suggest – otherwise you’ll end up slicing the sweet potatoes and onions with a sharp knife and the slices will be too thick (and they will not bake consistently) to make this gratin just perfect.

All you need to do is slice the sweet potatoes and the red onion with the mandoline and layer them on top of each other in a baking dish then drizzle olive oil on top with some sea salt, pepper and cinnamon for a touch of sweetness. It really doesn’t get any easier than this for such a beautiful and delicious meal. It’s cozy, light and easy to digest and it’s comforting without the cheese and breadcrumbs. It’s also fantastic when served with the dairy-free cheese recipes in my cookbook, Eating Clean, for a dose of protein on top.

sweet potato and red onion gratin on a linen tablecloth

red onion and sweet potato gratin in a staub baking dish on a tan tablecloth

Sweet Potato + Red Onion gratin
Serves: 6
red onion and sweet potato gratin in a staub baking dish on a tan tablecloth

This is an easy side dish that can be served during the holidays or during the colder months as a hearty main dish with your choice of protein on the side.

Author: Amie
Recipe type: Entree



  1. Preheat the oven to 400 degrees F. Prepare a baking dish with olive oil using your hands to ensure the base and the sides are coated.

  2. With a sharp knife, remove and discard the top of each onion as well as one end of each sweet potato before you start using the mandoline to ensure you are slicing with a flat vegetable surface. Using a mandoline (link above to the brand I recommend), slice the sweet potatoes and red onion into thin slices.

  3. Layer the sweet potato and red onion slices in the prepared baking dish (10.5" x 7.5") ensuring that the sweet potato layer is the top and final layer. Drizzle the top of the grain with olive oil, sprinkle with cinnamon, sea salt and pepper. Bake for 35 minutes covered with parchment paper then bake uncovered for another 10 minutes or until golden brown and the sweet potatoes and onions are very tender.

  4. Remove from the oven and set aside to cool for 5 minutes before serving. Serve warm.

  5. Store leftovers in a sealed glass container for up to 3 days in the refrigerator or up to 1 month in the freezer.

Nutrition Facts
Sweet Potato + Red Onion gratin
Amount Per Serving
Calories 154 Calories from Fat 1
% Daily Value*
Fat 0.1g0%
Saturated Fat 0.1g1%
Polyunsaturated Fat 0.03g
Monounsaturated Fat 0.01g
Sodium 85mg4%
Potassium 592mg17%
Carbohydrates 36g12%
Fiber 6g25%
Sugar 9g10%
Protein 3g6%
Vitamin A 21379IU428%
Vitamin C 8mg10%
Calcium 66mg7%
Iron 1mg6%
* Percent Daily Values are based on a 2000 calorie diet.

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