Squash, Potato & Caramelized Onion Tart
A warm and cozy savory tart on a rainy day with candlelight and the fireplace going is about as good as it gets. I made this Tuesday night as the "bomb cyclone" (a weather phenomenon I’d never heard of until now) was preparing to hit the West Coast and hoped that the power didn’t go out before my tart was baked. Thankfully, we didn’t lose power. (More on the storm below.) Anyhow, in anticipation of the storm, I was safe and warm in my kitchen making this cozy tart with rain and hail pounding on all four sides of the house. A beautiful thing about this colorful tart is that you can make it your own with your choice of sweet or russet potatoes and any mix of fall squash such as butternut, honey nut, acorn, delicata, or acorn. You could serve roasted chicken alongside the tart, but really it could be dinner on its own with a crisp green salad and a glass of wine.
Squash, Potato & Caramelized Onion Tart
I’d seen several fall squash tarts online, but ended up going with this recipe from Isabelle Heikens that my daughter had forwarded to me after she ate it at a Friendsgiving party. She made it in a 12” tart pan but the only tart pan with a removable bottom that I own is a standard nine-inch pan, which worked just fine.
My rainy day tart: Sweet potatoes, russet potatoes, butternut squash on a layer of caramelized onions in a peppery parmesan crust.
Read the entire way through the recipe before making! I say this mostly so you know that it takes an hour and 20 minutes in the oven plus the prep time and cooling time!
Crust ingredients
1⁄3 cup (60g) cornmeal
1 1⁄4 cups (180g) flour
1 1⁄4 cups (75g) parmesan
1 tsp kosher salt
1 tsp sugar
1 1⁄2 tsp freshly ground black pepper (it’s pretty peppery, so use less if you’d like)
1 stick salted or unsalted butter (doesn’t matter)
Filling ingredients:
2 medium yellow onions
1 large garnet sweet potato
1 butternut squash
1 large russet potato
3/4 cup gouda cheese, grated
Handful of fresh thyme leaves
1⁄2 stick salted butter, melted
Salt and sugar
Directions:
1. Preheat the oven to 350°F.
2. Prep all the veggies. The potatoes, onions and squash should all be sliced very thin. I don’t own a mandolin and am somewhat afraid of slicing my finger off with one. So I used my food processor to do the slicing. Cut your potatoes and squash into sections and place into the processor so that it will give you halfmoons. I did go back and manually cut some of the pieces in two afterwards. Slice one item at a time and separate in individual bowls.
2. Caramelize the onions: Heat a cast iron skillet over medium heat and add a few tablespoons of butter. Add the onions and a good pinch of salt. Stir every so often. Once they become translucent and start to brown, lower the heat to medium low. Continue to stir off and on as you make your crust. Once they are a nice brown color and are breaking down a bit, remove from the heat. You can add a splash of broth or water if needed. Set aside when happy with your onions.
Look at hose caramelized onions. Yum.
3. Make the crust. I made the crust as written and still used it all in my (smaller) pan, so it was thicker but still worked just fine. I think you could sub whole wheat flour for the cornmeal if desired, but I liked the texture the medium grind cornmeal gave it.
Melt 1 stick of butter in a pan and pour into a small bowl to cool. Note: You’ll need more butter later in the recipe, so go ahead and melt an additional 1/2 stick now in the pan you just used for the previous 1 stick of butter.
In a medium bowl, combine the cornmeal, flour, grated parmesan, salt, sugar, and black pepper. Pour in the melted better and stir to combine. You’ll most likely need to use your hands to push the dough together, slightly kneading it. If you find you still have bits of flour, you can add more melted butter a few drops at a time. (see note in previous paragraph.)
When the dough is mixed well and resembles damp sand, dump it gently into your tart pan (with a removable bottom). Push it up the sides and along the bottom of your pan to form the crust. Use the edge/bottom of a measuring cup to flatten it out as evenly as possible. Go back with your fingers or knuckles and make sure the crease where the sides and bottom meet isn’t too thick. It should be the same thickness as the bottom.
Prick the bottom of the crust all over with a fork. Then place tart pan on a baking sheet and bake in the 350 oven for 15 minutes. Remove from the oven and leave the tart on the baking sheet.
4. Fill the tart. Spread the caramelized onions across the bottom of the tart shell. Evenly sprinkle on the grated cheese and half of the fresh thyme leaves over the onions. Arrange the potatoes and squash slices in a circle over the top of the onions, starting with the outside and working your way toward the middle. This recipe from Constellation Inspiration, which was the other one I considered making but didn’t have miso in my pantry, has some great photos of how to arrange veggies on a tart. But really there’s no right or wrong way. Be your own artist.
Before she went back into the 350 degree oven.
Brush the squash and potatoes generously with the reserved 1/2 stick of melted butter. Season all over with kosher salt. Return tart to the 350 degree oven and bake for 1 hour. After 1 hour, remove from the oven and lightly sprinkle with a bit of sugar to help caramelize the edges. Then return to the oven for 20 minutes. I suggest testing the firmness of the potatoes and squash with the edge of a paring knife. If it’s too firm for your satisfaction, put back in the oven for a few minutes. Once it’s done to your liking, remove from oven, sprinkle with the remaining thyme leaves and some flaky sea salt if desired.
5. Remove tart from pan and serve — after you let it cool on a rack for 10-15 minutes. Then carefully remove the tart from its pan and place on a cutting board or large plate. before cutting into it. I’m here to tell you that it was still hard to slice without breaking up the crust and making a bit of a mess. Maybe I should have used a serrated knife. The second day, I cut it cold straight from the fridge and warmed it up in the oven covered with foil.
The tart was much easier to cut the next day when it was cold. Check out the layers.
The tart was just what nature called for on this stormy evening. Perfect for a cozy night in with the rain pounding outside all around us.
If you’re wondering about the storm, as were several friends who texted with concern about us living on the coast (thank you) — we experienced a ton of rain, copious amounts of loud hail and quite the thunder and lightning storm but basically came away unscathed. The waves were and are still angry, but the wind gusts didn’t seem to be as strong as predicted. However, the storm hit way harder inland in Washington state than it did at my beach town. Trees are down everywhere, and there are widespread power outages in the Seattle area.
I hope everyone stays safe and warm. I’d send you a savory tart if I could.