Caramelized Onion, Butternut Squash & Sweet Potato Sourdough Tart with Rosemary & Fried Sage

- Amanda

That name is a mouthful, I know, but I just had to do this tart justice. It’s got a lot going on in all the right ways. A rosemary sourdough crust with just the right amount of tangy yum, earthy, colorful and slightly sweet butternut squash and sweet potatoes kissed by a little more rosemary. Then utterly scrumptious caramelized onions mixed with not one, but three different types of cheese- gouda, parm, and creamy ricotta. This Caramelized Onion, Butternut Squash & Sweet Potato Sourdough Tart with Rosemary & Fried Sage makes for one stellar meal served with a little side salad or is a star addition to any holiday spread.

Let’s start with this Rosemary Sourdough Crust. As long as you have some starter discard, or a few minutes to make one, you can put this crust together. It starts with some flour, a little sugar, salt and some dried rosemary given a quick blitz in the food processor. Then some cold, cubed butter gets pulsed in until evenly crumbled. The starter and a dash of vinegar get added in next until it just starts to come together. You’ll finish it up on the counter and form it into a disc to chill until you’re ready to roll it, line it in the tart pan, dock it and give it a quick pre-bake for 10 minutes.

Next, comes the caramelized onions. I used a sweet yellow as well as a red onion for variation. Then let them sizzle softly in some olive oil for about 25 minutes until soft and gorgeous, and then add in a little minced garlic until fragrant.

Then you’ll prep the beautiful jewel-toned slices of butternut squash and sweet potatoes. I actually used one purple sweet potato and one yellow yam, but your store might call that a sweet potato as well. Sweet potato- patato, use what you’d like. I sliced mine mostly in rounds, with some of the squash being more half moon-like slivers. But as long as they’re all about an 1/8th of an inch thick, you can slice them any way you want. Then give them all a gentle toss in a little olive oil, salt, pepper and chopped rosemary.

Once your onions and squash and potatoes are prepped and waiting, it’s time to mix up some gouda, parmesan, and ricotta with some salt and pepper. Then the slightly cooled, caramelized onions get stirred into that. And you’re ready to start assembling.

And all that means, is layering the cheese and onion mixture on the bottom of the crust, followed by a layer of the squash and sweet potatoes, and then repeat two more times for each. Give the top a little drizzle of some evoo and another dash of salt and pepper. And into the oven it goes for about an hour and 15 minutes until it’s golden and beautiful.

And to finish it off, fresh sage leaves get a quick (less than a minute) fry in a little olive oil while the tart bakes. Then garnish the slightly cooled tart with the sage and dig in and enjoy.

I hope you give this recipe a go this holiday season. Lunch, dinner, even brunch, it works for them all. And if you do, I’d love to hear how it goes.

Happy weekend everyone.

*This recipe was created as part of the #sourdoughmonthlychallenge for this month’s theme of pie crust, hosted by @mgracebakeshop and @asoulfulkitchen. Check out the hashtag above for more awesome sourdough inspo.

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Caramelized Onion, Butternut Squash & Sweet Potato Sourdough Tart with Rosemary & Fried Sage

Prep Time 45 minutes
Cook Time 1 hour 15 minutes
Servings 8
Author Amanda – A Treat Life

Ingredients

For the Rosemary Sourdough Crust

  • 1 1/2 cups (192g) all-purpose flour
  • 1 tsp kosher salt
  • 1 tsp granulated sugar
  • 1 tsp dried rosemary
  • 6 oz cold butter, cubed
  • 1 tsp apple cider vinegar
  • 3/4 cup (187g) sourdough starter discard

For the filling:

  • 2 tbsps extra-virgin olive oil
  • 1 lg red onion, thinly sliced
  • 1 medium yellow onion, thinly sliced
  • 3 cloves garlic, minced
  • 1-2 tbsps extra-virgin olive oil
  • 1/2 large butternut squash, sliced about 1/8" thick
  • 1 medium yam, sliced about 1/8" thick
  • 1 medium purple sweet potato, sliced about 1/8" thick
  • 1 sprig fresh rosemary, leaves removed & chopped
  • 4 oz gouda, shredded
  • 4 oz ricotta
  • 2 oz grated parmesan
  • 1/2 tsp kosher salt
  • 1/4 tsp fresh ground pepper
  • 1 tbsp extra virgin olive oil
  • 8 sage leaves

Instructions

For the crust: (preheat oven to 350F/ 180C)

  1. Add the flour, salt, sugar and rosemary to the bowl of a food processor and pulse a few times to combine. Then add the cold cubed butter and pulse until it becomes a coarse meal. Then add the vinegar and the starter and pulse a few times until the dough just starts to come together with some crumble still.

  2. Pour the dough out onto a clean work surface and press the dough together until it forms a disc. Wrap it in plastic wrap and set in the fridge to chill for at least an hour. (Roast the squash while the dough is chilling.)

  3. After the dough has chilled, roll it out between two pieces of parchment paper to a little over 13 inches in diameter and about an 1/8th of an inch thick then carefully place it over the tart pan and press it into the sides and corners. Then use a rolling pin to roll over the surface of the tart pan to trim off the any edges hanging over the sides. Dock the bottom of the tart all over the bottom with the tines of a fork and set in the freezer to chill for 15 minutes.

  4. Then pre-bake the docked tart shell in the 350-degree oven for 10 minutes. Remove and let cool on a wire rack

For the filling:

  1. Preheat the oven to 375F/190C.

  2. Heat 2 tablespoons oil in a large saute pan over medium heat and add all the sliced onions and stir to coat the onions with the oil. Spread them out evenly over the pan and let cook. Reduce the heat to medium-low and cook, stirring occasionally, for a total of about 20-25 minutes until they are nice and dark blonde and deep purple-colored. Then add the minced garlic and cook a minute or so more until fragrant. Set aside.

  3. Then toss the sliced butternut squash, yam and purple sweet potato with the 2 tablespoons of oil, chopped rosemary and a pinch of salt and pepper.

  4. In a medium bowl stir together the shredded gouda, ricotta, parmesan and salt and pepper. Then fold in the slightly cooled caramelized onions.

To Assemble:

  1. Line the bottom of the pre-baked tart shell with about a third of the onion/ cheese mixture and spread evenly. Then lay out a layer of the squash and sweet potato slices. Then repeat with two more layers of the cheese mixture and two more of the squash, ending with the squash. Drizzle a tiny bit of olive oil over the top of the tart.

  2. Bake until golden brown and the squash is tender, about 1 hour- 1 hr 15 minutes.

  3. While the tart is baking, coat the bottom of the pan you used for the onions with extra-virgin olive oil. Then heat until shimmering. Add sage leaves in a single layer and fry for about 30 seconds to a minute. Remove with a slotted spoon and transfer to a plate lined with paper towels and sprinkle with a little kosher salt.

  4. Let the tart cool for about 10-15 minutes, top with the fried sage leaves and enjoy.

Recipe Notes

*The dough can be prepped a few days in advance, wrapped tightly and kept in the refrigerator.