Prep the oven and pan: Preheat your oven to 350°F (175°C). Lightly grease an 8x8-inch baking dish or similar.
Make the strawberry base: In the baking dish, toss sliced strawberries with 1/4 cup sweetener, lemon juice, lemon zest, and vanilla. Spread into an even layer.
Mix the dry topping: In a bowl, whisk almond flour, coconut flour, remaining 1/4 cup sweetener, baking powder, salt, and cinnamon.
Add fat for crumble texture: Stir in the melted butter and heavy cream (if using) until the mixture forms moist crumbles.
It should clump when pressed.
Assemble: Sprinkle the crumble evenly over the strawberries. Don’t pack it down. Scatter nuts on top if using.
Bake: Bake for 25–35 minutes, until the fruit is bubbling and the topping is golden brown.
If the top browns too fast, tent loosely with foil.
Rest and serve: Let it cool for 10–15 minutes to set. Serve warm with a spoonful of whipped cream or a keto ice cream scoop.