Preheat your oven to 350°F. Line a 9x13-inch baking pan with parchment paper or lightly grease it.

I usually leave extra parchment hanging over the sides because it makes lifting the bars out way easier later. The first time I skipped this, I ended up struggling to cut clean squares directly in the pan.

In a large bowl, mix flour, granulated sugar, brown sugar, baking powder, and salt. Add cold cubed butter and work it into the dry ingredients using your hands or a pastry cutter until it looks like coarse crumbs.

Then mix in the egg and vanilla extract. The dough should look crumbly but hold together when squeezed. I noticed if the butter gets too warm, the texture changes and becomes more dough-like than crumbly.

In a saucepan over medium heat, combine strawberries, rhubarb, sugar, cornstarch, lemon juice, vanilla, and salt.

Stir gently as it cooks. After about 8–10 minutes, the mixture starts to soften and release juices. The smell at this stage is really good—sweet strawberries mixed with that sharp rhubarb tang.

What worked better for me was cooking it until it thickens slightly but still looks a little glossy. If it gets too thick, the filling turns more like jam and doesn’t spread nicely in the bars.

Press about two-thirds of the crumb mixture into the bottom of your prepared pan. Press it firmly so it forms a solid base.

I usually use the bottom of a measuring cup to even it out. It helps keep the layer consistent so the bars bake evenly.

Spread the strawberry rhubarb filling evenly over the crust. Try to get it into all corners so every bite has fruit.

Don’t worry if it looks a little loose at this point—it sets up while baking.

Sprinkle the remaining crumb mixture over the top of the fruit layer. It doesn’t need to fully cover everything. Some gaps are totally fine and actually look more homemade.

Bake for 40–45 minutes, or until the top is lightly golden and the filling is bubbling slightly around the edges.

The kitchen usually smells like warm fruit jam and butter at this point. It’s hard not to peek early, but I noticed the bars need the full time to set properly.

This is the hardest step. Let the bars cool in the pan for at least 2 hours.

If you cut them too early, the filling will be too soft and messy. I learned that the hard way when I tried serving them warm for guests and ended up with more spoon dessert than bars.