Preparation

• Preheat your oven to 350°F and line a 9x13 inch baking dish with parchment paper. While the oven heats, measure and prepare all your ingredients: slice the rhubarb into ½-inch pieces, hull and slice the strawberries into ½-inch pieces, roughly chop the cashews into ¼-inch pieces, and zest the lemon. Having everything ready before you start mixing ensures smooth assembly and prevents the base from over-baking while you're still prepping.
• In a bowl, combine the almond flour, coconut flour, and salt. Add the vanilla, maple syrup, and cooled melted coconut oil, stirring until the mixture resembles wet sand and comes together. Press three-quarters of this mixture firmly and evenly into the prepared baking dish, creating an even layer about ¼-inch thick. Bake this base for 10-12 minutes until it turns light golden—it should be partially set but still slightly soft.
• While the base bakes, add the sliced rhubarb and strawberries from Step 1 to a saucepan along with the lemon juice, maple syrup, and salt. Bring to a simmer over medium heat and cook for about 7 minutes, stirring occasionally, until the fruit softens and releases its juices. The mixture should break down slightly but still retain some fruit texture.
• In a small bowl, whisk together the water and tapioca starch until smooth with no lumps. Stir this slurry into the fruit mixture and add the ground ginger, cooking for 1-2 minutes more until the sauce thickens slightly and the raw starch flavor is cooked out—it should coat the back of a spoon but still be pourable.
• Remove the pre-baked base from the oven and pour the thickened fruit filling over it, spreading it into an even layer. Crumble the cashew dough mixture from Step 4 evenly over the fruit filling, leaving some texture rather than pressing it down—this creates nice crunchy bits on top. Return to the oven and bake for 20 minutes until the top is golden and set.
• While the bars bake, warm the coconut butter until it's smooth and pourable, then stir in the maple syrup, vanilla, water, and lemon zest until you have a drizzleable glaze with a smooth consistency. Remove the baked bars from the oven and let them cool for 10-15 minutes so the glaze will set slightly rather than soak into the hot bars. Drizzle the glaze over the cooled bars in a thin, decorative pattern.