Preheat the oven to 350 degrees.
Add the crust ingredients in a food processor - hazelnuts, cashew meal, maple syrup and almond milk. Process until all ingredients are combined.
Press the crust mixture evenly into a 9x9 baking dish. Bake the crust for 20 minutes, until lightly brown on the edges.
While the crust is baking, chop the strawberries and rhubarb stalks into small pieces.
Whisk 4 eggs until combined. Add the rest of the custard ingredients and mix well - flour, salt, vanilla, chopped strawberries, and rhubarb.
Add the custard on top of the pre-baked crust.
Bake for 30 minutes.
Let the bars cool slightly before cutting. Keep the leftover bars refrigerated.