Prep the pan and oven: Preheat your oven to 350°F (175°C).
Line an 8-inch round cake pan with parchment and lightly grease the sides. An 8x8-inch square pan also works.
Mix the dry ingredients: In a large bowl, whisk almond flour, coconut flour, baking powder, salt, and the granulated sweetener. Break up any almond flour lumps with the whisk to keep the batter smooth.
Combine the wet ingredients: In another bowl, whisk the eggs until slightly frothy.
Add Greek yogurt, melted butter, almond milk, vanilla, and almond extract. Whisk until fully combined and silky.
Bring it together: Pour the wet mixture into the dry ingredients. Stir with a spatula until just combined.
The batter will be thick but spreadable. If it looks dry, add 1–2 teaspoons more almond milk.
Fill the pan: Scrape the batter into the prepared pan. Smooth the top with an offset spatula.
Sprinkle sliced almonds on top for crunch and a pretty finish.
Bake: Bake for 28–35 minutes, or until the top is golden and a toothpick inserted in the center comes out mostly clean with a few moist crumbs. Check at 28 minutes to avoid overbaking.
Cool: Let the cake cool in the pan for 10 minutes, then run a knife around the edge and lift out using the parchment. Transfer to a rack to cool completely.
Almond-flour cakes set as they cool, so give it time.
Finish and serve: Dust lightly with powdered erythritol if you like. Serve plain, with a dollop of whipped cream, a spoon of berries, or a drizzle of sugar-free chocolate.