Preheat the oven to 375°F.
In a medium bowl, mix chopped rhubarb with 2 Tbsp monk fruit sweetener.
In another bowl add blueberries and mix with 1 Tbsp monk fruit sweetener. Let both fruit mixtures sit for 10 minutes while you prepare the topping.
For the topping, combine almond flour, oats, diced butter, 1/2 cup monk fruit sweetener, cinnamon, and salt to a food processor and pulse until it takes a crumbly texture.
Drain any extra juice from the fruit bowls, and combine both fruit mixtures into one larger bowl with cornstarch, lemon juice, and vanilla until thoroughly mixed.
Layer the fruit on the bottom of an 8X8 pan, then top with the crumble mixture
Bake for 40 minutes or until the fruit is bubbling and top is a light golden brown.
Remove from oven and let cool for 30 minutes before serving. Enjoy!