• Preheat the oven to 325°F.

Crust:

• In a mixing bowl, stir together the almond flour, butter, brown sugar, tapioca starch, and salt until well combined. Transfer the mixture into a 9-inch springform pan and press into the bottom, pressing it up the edges a little bit if you’d like. Set the pan on a baking sheet and transfer to the oven. Bake until lightly browned and dry to the touch, 15 to 20 minutes. Cool.

Cheesecake:

• While the crust cools, combine the cream cheese, cottage cheese, and sugar in a blender or food processor, and process until smooth. Add the eggs, tapioca, starch, extract, and salt, and blend until smooth. Stir in the blueberries.
• Pour the mixture into the springform pan over the crust. Tap it a few times on the counter to eliminate air bubbles. Transfer to the oven and bake for 50 to 60 minutes, until just set in the center. Turn off the oven, crack the oven door open, and let the cheesecake cool for 30 minutes in the oven. Then cool completely on a wire rack at room temperature.

Topping:

• To make the topping, combine about two thirds of the blueberries, maple syrup, lemon juice, and salt in a saucepan. Bring to a simmer and cook until the juices thicken, 8 to 10 minutes. Make a slurry by whisking together the tapioca starch and water, then pour it into the sauce along with the remaining berries. Cook for 30 to 60 seconds, then remove from the heat and cool completely.
• To serve, run a thin knife around the edge of the cheesecake and unmold from the springform pan. Spread the berry sauce evenly over the top of the cooled cheesecake. Wipe your knife clean between each cut to get clean slices.