Just like my peach crumble bars, these delicious rhubarb bars with a crumble topping are vibrant in color and flavor, and taste like summer! And ridiculously easy to make too. These rhubarb crumble bars have also been making an appearance in my kitchen repeatedly over the last month, and summer has only just officially begun! But the great thing is that you can easily adapt these dessert bars into strawberry rhubarb bars with a crumble topping, to make use of all the gorgeous strawberries available in summer as well. These are such fantastic fruit desserts to enjoy all summer long. These rhubarb bars start with a homemade rhubarb filling that is similar to a jam. I add some apple to the filling, purely to help thicken the filling properly to a jam-like consistency WITHOUT adding too much sugar. This jam is then spread between a buttery shortbread layer and a crumb topping that is made with the SAME dough! So you end up with a delightfully buttery, tart rhubarb bar that has just the right amount of sweetness! The red rhubarb stalks will obviously produce a prettier color, but there won’t be a difference in taste. If you like though, you can substitute some of the rhubarb with some strawberries for flavor and color.
Green apple
You CAN leave this out if you like. But I LOVE the additional tart flavor and jammy texture that apples add to the filling.
Sugar
I use white sugar so that the flavor of rhubarb can shine through. I prefer not to use brown sugar for this recipe.
Lemon juice
The fruity acidity from lemon juice will brighten up the filling flavor for a more summery rhubarb bar!
Egg
I add an egg to this recipe to act as a binder. As a result, the shortbread base isn’t too crumbly and will hold together very well.
Sugar
I use caster sugar (white), so that the sugar will dissolve more readily in the dough, but you can use granulated sugar as well.
Flour
All purpose flour is ideal for this rhubarb recipe. You can use cake flour if you like and if that’s all you have. But avoid using bread flour, since the high gluten content in bread flour can make the shortbread tough.
Flavoring
Vanilla and salt are the only flavoring that I add to the shortbread base. You could also add a little almond extract if you like. Personally, I do not like almond extract however.
Optional topping ideas
The shortbread dough for the topping can be mixed with chopped nuts or other additions to make the crumble topping for your rhubarb crumble bars more interesting. This is optional though. Here are some ideas,
Almond slices Walnuts Pecans Coconut (desiccated or flakes) Cashew nuts Oats Puffed quinoa
Wash and dry the fresh rhubarb and cut them into 1 inch pieces. Place the rhubarb in a large pot, along with the sugar, grated apple, lemon juice and water. Cook over medium heat while stirring. The mixture will come to a boil and then thicken into a jam-like, thick consistency, almost like apple butter. The total cook time for me is between 35 – 40 minutes on low heat. Place the rhubarb filling in a bowl or container and let it cool until it’s at room temperature. You can use it if it’s just a little warm, but not too warm, as it will melt the butter in the shortbread layer. You can also chill the jam for up to 5 days before you use it. In a large bowl combine the dry ingredients first. Then add the wet ingredients into the same large bowl. Mix well using a spatula or even your hands. I use my hands because it’s faster and easier. You should end up with a soft ball of dough. Make sure NOT to overhandle the dough because it will make the dough too tough. You should end up with a dough that looks like this. Separate the dough into two uneven portions – about ¾ and ¼. The ¾ portion will be used as the base, and the ¼ portion will be used for the topping. Take the ¾ portion of dough and press it evenly into the baking dish. Use a flat surface to help press and level the layer. Next, take about 1 cup (it’s OK if it’s slightly more!) of the rhubarb jam filling and spread it evenly over the shortbread base. Take smaller pieces of the leftover dough and flatten slightly. Place these slightly flattened pieces of dough on top of the jam layer to create the crumble topping. You can choose to put as much as you like to cover the jam in a thin layer of the shortbread dough, OR leave some gaps for the jam to peek through (like I did here in these pictures). Remove the pan from the oven after baking and let it cool to room temperature, OR you can place it in the fridge overnight to chill the bars. They are definitely easier to cut when a little cold, but I won’t blame you for not wanting to wait until the rhubarb jam bars are chilled and ready! 🙂 To make strawberry crumble bars – Replace the rhubarb topping with this homemade strawberry jam instead. Vegan options – Replace the butter with a vegan butter (not margarine) and instead of the egg, use about ¼ cup of plant-based milk to bring the dough together.
Can I make these rhubarb bars ahead of time?
Yes! The jam can be made weeks in advance, but you have to freeze the rhubarb jam until you need it. Then just thaw it before you spread it on top of the shortbread layer. The dough can also be made ahead of time, but it’s so easy and quick to assemble, that I never really bother making it ahead of time. But if you like, here is how you can store the dough if you don’t want to make the bars right away. Make the dough and flatten it into a disc. Wrap and store in the fridge for up to 2 days. When you’re ready to use it, let it soften slightly, and then remove about ¼ if the dough and set that aside for the topping. Then proceed with the recipe instructions for assembly. My preference however is to make the rhubarb bars, bake them, and then store those for later instead!
Storage instructions
Once the bars have cooled down, cut them into squares or bars (however you like). I usually cut them into 4 x 4 pieces (16 squares). Make sure to use a sharp knife to get those clean edges. Store the bars in an air-tight container. Room temperature – about 2 days Fridge – about 1 week Freezer – about 2 months. If you’re storing them in the freezer, make sure to separate stacked bars with parchment paper to prevent them from sticking to each other. I also highly recommend that you wrap them in foil before storing it in an air-tight container. I find that this practice reduces the buttery shortbread from absorbing other smells from the freezer.
Tips for perfect rhubarb bars
You don’t HAVE to make the rhubarb topping in advance! Once you make the topping, spread it out on a quarter sheet pan and place it in the freezer or fridge to cool it down faster. You can use red OR green rhubarb. It’s also a great recipe to use up rhubarb that’s a little bruised or wilted. You can also use frozen rhubarb to make the filling, if fresh rhubarb isn’t available. Make sure to use a kitchen scale for the ingredients (especially for the shortbread dough). Adding too much flour can result in a dry and crumbly shortbread crust.
