Rhubarb Thumbprint Cookies
Thick & chewy sugar cookies filled and baked with homemade vanilla rhubarb jam.
These thumbprint cookies have a homemade rhubarb jam added to the center for a deliciously sharp filling. The vanilla adds a touch of sweetness to the jam, and there’s a little lemon a touch of tart to the cookies!
As soon as I saw rhubarb in the store for the first time this season, I knew what I wanted to do. I prefer to incorporate rhubarb by first cooking it down, pureeing and discarding the stringy bits (I hate those bits) like in these blueberry shortbread bars or these oatmeal rhubarb bars. Once I had this delicious puree (coulis? We’re calling it a jam for simplicity’s sake & so it is in theme with the thumbprint cookie), I debated doing another bar but oh, a cookie sounded like a fun new adventure.
Recipe Origins
This recipe has roots in two existing blog recipes: my lemon curd cookies (the dough is the same) and the rhubarb jam is adapted from these oatmeal rhubarb bars; I swapped the raspberries for more rhubarb so we could stay true to the uniquely sharp rhubarb flavor.
Recipe Ingredients
Rhubarb: fresh rhubarb with the leaves and bottoms discarded.
Sugar: fine granulated sugar.
Starch: cornstarch or tapioca starch; this is to thicken the rhubarb filling.
Salt: fine sea salt or fine kosher salt. If using table salt, use half the amount.
Vanilla: a vanilla bean for the rhubarb filling (this is optional, you can also just add vanilla to the puree after cooking) and pure vanilla extract or vanilla bean paste for the cookie dough.
Butter: unsalted butter or salted; if using salted reduce the amount added to the dough.
Powdered sugar: made with tapioca starch preferably, but cornstarch works too (check the label). It should be sifted to remove any lumps.
Egg: one whole large egg, at room temperature.
Baking soda: to leaven the cookies.
Flour: all purpose flour of a medium protein content, around 11%. A lower protein will lead to flatter cookies!
How to make Rhubarb Thumbprint Cookies
Make the rhubarb filling
Note: this makes double what you need for the cookies, I think it’s easier to make these things in big batches but if you don’t want extra make half the batch. Leftovers can be used on ice cream, french toast, pancakes … .etc., anywhere you’d use a spread or coulis.
Chop the rhubarb and set it and the jam ingredients in a pot over low to medium heat. If using a vanilla bean, slice it lengthwise, scrape it and add the whole bean and the scrapings to the jam.
Stir occasionally, as the rhubarb cooks and softens.
Once the rhubarb has completely broken down, use an immersion blender to puree it. Alternatively you can transfer it to a blender or a food processor to puree.
> I hate the stringy bits of rhubarb so I press this puree through a fine mesh sieve to remove those bits. Even if you like or don’t mind them, I don’t recommend keeping them because the rhubarb jam itself will be harder to neatly fill into the cookie.
If you aren’t scraping and adding a whole vanilla bean to the jam but you’d like to add some for flavor, add it after the jam has cooked.
Let cool then set in the fridge for at least a few hours but preferably overnight and up to a week – in an airtight container.
Make the cookie dough
Set the granulated sugar in a heatproof bowl (we’re microwaving it in a bit) and if using lemons, zest them over the sugar then rub the zest into it using your fingers.
Add the butter to the bowl and either use the sugar to cover the butter or a microwave plate (so the butter doesn’t sputter out) and heat for 60 seconds, to melt the butter.
Add the salt and vanilla and whisk very well.
Sift in the powdered sugar and whisk until well combined, at least 30 seconds.
Crack in the egg and whisk well.
Add the flour and baking soda and stir until the mix is well combined. Cover with plastic wrap and set the dough in the fridge for 3-4 hours, or overnight.
Shape the cookies & bake
Preheat the oven. Grease two cookie sheets and place a sheet of parchment on them.
Scoop the cookie dough in rounds onto the prepared sheets; leave enough room for them to spread.
Press the bottom of a rounded tablespoon into the center of the cookie (or use your thumbs) – ensure you have a perfect bowl indentation in the center, without cracks.
Pour about half a tablespoon of the rhubarb jam into the center. Check again for cracks and patch up any areas where it looks like the filling might seep out.
Bake the cookies for 12 minutes, until the edges are just turning golden.
Let cool on the pan. Before serving, dust with powdered sugar (if you like!~)
FAQ
Can I make these ahead of time?
The ‘jam’ filling can be made up to a week ahead of time. The dough for the cookies should be made a few hours before but can be made the night before. I wouldn’t suggest leaving the dough in the fridge any longer or it will dehydrate.
Once baked and cooled the cookies can be frozen in an airtight container, but take care layering them with parchment paper so the fillings don’t stick to anything.
Can I double the recipe?
If you’d like more cookies you have enough jam to fill two batches of the recipe below (so x2 everything). If you want more than around 22 cookies, you’ll need to make more jam!
Why am I making double the amount of rhubarb jam for the cookies?
I find it easier to bake bigger batches of jam so it’s on hand for multiple uses. If you don’t want it for anything but the cookies and you’re only making the recipe below, feel free to halve the recipe. Cook time will be less for the jam.
My cookies made a mess – the jam spilled out. How can I prevent this in the future?
Once the filling is in the cookie dough, check to make sure there are no cracks around the center where the filling is – those little cracks or divots is where the jam will spill out of. Use extra dough to patch it up neatly.
My cookies didn’t spread or spread too much. What went wrong?
If you used cups, the flour might have been over-measured (if they didn’t spread) or under measured (if they spread too much). A low protein flour will also cause over-spreading as will a too warm dough.
Rhubarb Thumbprint Cookies Recipe
Rhubarb Thumbprint Cookies
Ingredients
Rhubarb Jam (makes double what you need for the cookies - halve the recipe if you don’t want leftovers)
- 400g g rhubarb chopped (about 3 large stalks), weighed after stems and leaves removed
- 120g fine granulated sugar about ½ cup plus 2 tablespoons
- 1 ½ tablespoons tapioca starch or cornstarch
- Pinch fine sea salt
- 1 vanilla bean split (optional)
Cookie Dough
- 200 or 1 cup cup granulated sugar
- zest of 2 lemons
- 226g or 1 cup butter unsalted
- 2 teaspoons pure vanilla extract
- 1 teaspoon fine sea salt
- 65 or ½ cup powdered sugar
- 1 large egg
- ½ teaspoon baking soda
- 390g or 3 cups all purpose flour if using cup measurements, shake the flour over the measuring cup and level it - never pack it in
- Powdered sugar for sprinkling on top if desired
Method
Make the Rhubarb Filling (can be done up to a week ahead of time)
- Remove the leaves (any green part) from the rhubarb and chop into 1 inch pieces. Set a pot over medium low heat and to it add the rhubarb, sugar, starch, salt and vanilla bean, if using (for the vanilla bean: slice the bean down the middle and pry the sides open like a book, scrape down to gather the caviar and add the bean and it’s scrapings to the pot).
- Cook slowly, stirring occasionally to ensure the rhubarb doesn't burn at the bottom of the pan. As it cooks the rhubarb will break down, once it’s very soft remove the vanilla bean pod and puree the mix (you can do this with an immersion blender right in the pot or transfer to a food processor or blender). Press the puree through a fine mesh sieve, take your time doing this and squeezing out all the fruit while leaving the stringy bits behind.
- Transfer to an airtight container and store in the fridge for at least a few hours before using but up to a week.
Make the Sugar Cookie Dough: should be done at least 3-4 hours before baking the cookies, or overnight
- Set the granulated sugar in a heatproof bowl and zest the lemons over it. Rub the lemon zest into the sugar with your fingers. Set the butter in the bowl and place it in the microwave for 60 seconds (use a microwave plate to cover the butter so it doesn’t sputter out) until melted.
- Whisk the butter and sugar together vigorously. Add the salt and vanilla and whisk well. Sift in the powdered sugar then whisk until the mix is thick and cohesive.
- Add the egg and whisk well then stir in the flour and baking soda until the flour is all incorporated. Cover with plastic wrap (or transfer to an airtight container) and chill in the fridge for 3-4 hours or overnight.
Shape & Bake the Cookies
- Preheat the oven to 350 F and line two greased cookie sheets with parchment paper.
- Use a disher to scoop the cookies into about 2 tablespoons per cookie (you can make them smaller or bigger but they need to hold enough jam), ensuring you have a rounded ball and leaving enough space for them to spread. Press the cookie dough in the middle with a rounded tablespoon or your thumbs until you have a tiny bowl shaped indentation (careful not to go too deep that you have a too thin layer on the bottom of the cookie). Pour in about a half tablespoon of jam (or however much works for your chosen size of cookie). Round the cookies with your hands and add a bit of dough to anywhere a crack might appear; this way none of the filling seeps out in the oven.
- Bake for about 12 minutes, until the cookies are just turning golden on the edges. Let cool on a pan then transfer to a plate to serve. Before serving, sprinkle the cookies with powdered sugar, if desired.
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Should I add a teaspoon of vanilla to the jam since I don’t have a vanilla bean?
Yep, you can add it after the jam cooks and after you sieve it.